the following is a pretty good guide for determining the quality of PSU's. Credit goes to jonnyGURU for compiling this list. His website has changed and this list is no longer available on it. the link to the google cache is here

here is his list, with his color coded rankings:

RED is simply "not recommended" for any kind of performance system. These are power supplies that tend to be sold with nothing more in mind but price. Cheap, cheap, cheap.

VIOLET is the cream of the crop. That's not to say I expect you to run out and buy one off the violet list, but if you have a lot of money burning a hole in your pocket, you can't go wrong with VIOLET.

INDIGO was almost VIOLET, but I couldn't see putting Enhance and Enermax in the same category as Etasis and Zippy.

ORANGE is mediocre at best. Personally, I'm not installing one for anything I'm building/using. Typically the voltages printed on the label aren't accurate representations of what the power supply can do.. at least sustained power. At least they don't have the tendency to burst into flames.

YELLOW is Ok. In fact, my wife's PC has a yellow in it. But her PC is a Socket A with only a few drives and an nVidia 6800GT AGP card. Maximum 12V load on her machine is probably something like 18A, so getting a 500W with 24A on the 12V rail from the yellow list isn't necessarily a bad idea. I just wouldn't push one.

BLUE is quite good. In fact, 99% of the people out there are going to be perfectly fine with a power supply from the blue list. And GREEN? Well.. that's just between BLUE and YELLOW.

RED

* Deer (UL # E203196)
* Allied (UL # E214301)
* L&C (UL # E164554)
* Powmax & Diablotek (both made by Leadman)
* Dynapower (UL# E195877)
* Raidmax (the ones that come bundled with a Raidmax case. Not necessarily one you'd buy separately.)
* Rhycom (sometimes made by Sun Pro, but always?)
* Achieve/Viomax
* Turbo Links that are made by "Real Power" (like the ones that are included inside Aspire cases.)
* OKIA (comes in Broadway Com Cases. UL# E194657)


ORANGE

* Rosewill (various manufacturers, but usually fair quality.)
* Coolmax and some other ATNG manufacturered units. (UL# E186010)
* Low end Wintech's (like Ultra V-Series and some Turbo Links, UL# E178768)
* Other Aspires (despite source factory being a yellow, they over-rate all of their PSU's)


YELLOW

* FSP Saga series (AX part number. Sparkle's UL # is E161885. Fortron's is E190414)
* Youngyear (includes some older Ultra X-Connects, MGE's, etc. UL# E126556)
* A.C. Ryan (never figured out who builds them.)
* Enlight (used to be Enhance, but now seem to all be ATNG's)


GREEN

* TTGI/Superflower (UL# E242429)
* Topower P5 based units (like OCZ Modstream, Tagan, most ePowers. UL# E130843)
* Most Thermaltakes (Sirtech or Channelwell)
* Many Channelwell units (UL # E193705 or E161451)


BLUE

* Most Wintech (most Ultra models, Sintek, Future Power, some MGE's. UL# E178768)
* Topower P6 based units (like the OCZ Powerstream. UL# E130843 )
* AcBel Polycom (Coolermaster and Asus unit for example. UL# E131875 or E193721)
* Antec (Channelwell or Seasonic)
* PC Power and Cooling Silencer series
* Ablecom/Supermicro (UL# E193726)
* Andyson (Lower end models like Sunbeamtech and Aerocool. UL# E239028)
* Delta
* AMS Mercury
* FSP/SPI (those with FSP part numbers. Sparkle's UL # is E161885. Fortron's is E190414)


INDIGO

* SevenTeam (UL# E141400)
* Andyson (Higher end models like some Hiper and Ultra models. UL# E239028)
* Seasonic (UL # E104405)
* Enermax
* Enhance (includes some Silverstone units. UL# E166947)


VIOLET

* PC Power and Cooling Turbo-Cool series
* Zippy/Emacs (UL# E143756)
* Etasis (includes some Silverstone units. UL# E176239)

Now that we know the colors of the rainbow, let's throw something else out there... If you have a power supply in the GREEN category, I want you to take all of the values on your power supply label and multiply them by 90%. If you're in the YELLOW category, multiply by 85%. ORANGE, multiply by 75% and RED, multiply by 60%. We probably should take BLUE and multiply it by 95% too.

There's two reasons for this:

* There's a big difference between peak wattage and sustained, or continuous, wattage. I've learned different companies label power supplies differently.. even different models within the same manufacturer! Comparing labels is not an apples to apples thing.

Some power supplies are rated at "peak." For example; a Powmax Demon (which would be on the RED list) might be able to handle a 580W load in a split seconds time, but it can't maintain anything more than 350W for any period of time. A Topower P5 520W can sustain 520W, but I've found that once I get over 420W or so, the voltages start fluctuating wildly. I'll see as much as a .3V fluctuation on the 12V rail under a sustained load. The same is true with the Ultra V-Series I have. It's rated at 500W, and it can do 500W, but anything over 400W causes the rails to bounce around more than I like. The voltages may be within spec, but I don't feel comfortable with my voltages bouncing back and forth as much as 4%!

* The other discrepency would be due to the temperature at which the power supply was tested to obtain it's rating. Not to say that all power supplies (other than PC Power and Cooling) aren't all tested at the same unrealistic ambient temperature. But cheaper power supply's diminishing curve is greater than with a better unit. In other words, the capability of a cheaper power supply to provide good, clean power takes an exponential nose dive as the power supply heats up.

The BLUE and INDIGO are pretty much ONLY adjusted because of operating temperature. All of the units on those lists will maintain their voltages for at least half an hour (that's how long I hold my loads) ON MY BENCH, but won't necessarily hold those loads for that long if installed into a case where temperatures may get the best of a power supply.

Now all of the above is totally MY OPINION. There's NOTHING really scientific about any of the numbers I provided either. I haven't had a chance to review every power supply on the face of this Earth and even of the ones I have reviewed, everyone's results are going to vary.

That said; there are some common sense things to look for when shopping for a power supply... REGARDLESS of what I say.

* Look for a power supply with good efficiency. Cheap power supplies don't emphasize on efficiency. If you get something that's 70% or 80% efficienct or better, it's probably going to be at least a BLUE on my list. Unfortunately, most power supplies list their efficiency as > 70% even if they're just under 80% at 50% load. So you'll want to rely on a good review site to let you know what a power supply's efficiency is.

* Intel specifications for an ATX power supply allow for 5% tolerance on the primary rails. Despite this, I've seen some power supplies rate their power supplies with a 10% tolerance. What does this mean? Well.. most power supplies you can safely "overload," but the outcome is rails that are out of whack by as much as.. let's say... 10%. So in a sense, you could have what may very well be a 500W power supply with a 5% tolerance be labeled as a 600W power supply because they're allowing for a 10% tolerance at higher loads. My suggestion? Just stay away.

* If in doubt, look for a power supply that at least has active power factor correction as an option. Not that you necessarily have to spring for active PFC, especially if you live in the US. But I've found that cheap power supplies don't tend to have active PFC. From what I've seen, we're talking about power supplies that tend to at least fall into the GREEN category. YELLOW at the lowest and that's rare. If the active PFC model is a bit expensive, look for the same thing in a non-PFC model. Most manufacturers make their units in both flavors. You don't need GPS in your Lexus, but you can have piece in mind in knowing the Kia you passed up on didn't even have GPS as an option.

* Be VERY AWARE of what's on the label. If a power supply lists all of the rails and what amperage each rail is capable of doing.. what does that really tell you? You WANT TO KNOW combined wattages. If you have two 12V rails and each one does 16A, what good does that do you if you don't know what the COMBINED capability of those two rails is? What if the power supply can only put out 240W on the combined 12V rails?!?!

* Don't just look at price and assume a power supply is better than another. This is a BIG pet peeve of mine. All of the time I'll see someone say, "I have $100. I'm trying to decide between this power supply with the LED's and modular cables and this one that has 1 Gigawatt available on the 12V rail." You are an idiot. FEATURES AREN'T FREE! I've seen MANY power supplies that are plain jane in appearance that sell for a mere $60 that would wipe the floor with a $100 unit with modular cables and windows and lights. That's not to say you're not allowed to consider the $100 with all of the bling. I'd be a hypocrite if I told you a $100 power supply isn't worth $100 because of all of it's bling. But at least have enough common sense to compare apples and apples. If the bling isn't important to you, keep in mind that what you're looking at for $100 may only be worth $60 if it didn't have all of the bells, horns and whistles!

* Don't buy a power supply just because of it's looks! Yeah, LED's look cool and aluminum housings with windows sure seem like something you'd find only in a quality unit.. but you know the saying, "You can polish a turd...