Im sure this is a common misunderstanding, but is more wattage in a PSU perform any better? or does each component require a certain number of watts, and more is just more availability for additional components? If that is the case (which im almost positive it is, just making sure ) how much should i get with this setup:

Abit IC7-MAX3
1024mb Corsair XMS dual channel pc2700 ram
12v DC water pump
2 120mm fans
P4 3.00ghz prescott core
CD-RW drive
DVD-ROM drive
Two harddrives (maybe three in the near future)

I think tahts everything i have connected.... I am getting a really expensive PSU (one of those silenx ones...) so i dont want to have to upgrade it anytime soon. With 450W do me fine, or should i go with 520W? i dont plan to go any higher than 520W... note: i have no case fans hooked up, only the two 120mm fans.

THanks in advance and sorry for the noob post :-/

What video card?

radeon 9800 pro 128mb.. that too might be going upgraded...

my 350w power supply runs my comp (geforce 5600 ultra, 2 hd, 2 cd-roms, fans, etc) fine. A good 450w will be fine

Check the PSU FAQ thread. Lego posted a link to a PSU wattage calculator that help you determine your system needs.

It looks like you will have a pretty decent system except for one major boo boo. You p4 requires pc3200 to run at its full potential, not pc2700. Instead of the corsair, I'd look into some of these modules made by PDP. Here is a thread I started earlier for further details about the PDP memory. About the power supply, those silent X PSU's are pretty good and they are actually based on Sparkle/Fortron units. You would be fine with the Silent X, but they are a bit over-priced IMO. I'd rather go with this PSU made by Fortron. It should be able to power virtually any setup and is cheaper compared to the Silent X PSU's.

wow thanks lilkev!! however, the reason i am getting the silenx is for the silence... i dont think the forton is as silent.. 14dba is really quiet

Those silentX PSU's are quiet, but the rated 14db-A is more of a marketing gimmick IMO. I own the 530watt fortron myself and it is definately the quietest component in my case, I can barely hear it.

Wattage counts, but amps is also a big player in how many devices you can handle. I'd try and get something that has over 20a on the 12v rail. I have 34a on my Aspire 520w (very nice psu BTW) and it still has some droop issues with the 10 fans, 2 lights, 9800 Pro AIW, and massively overclocked CPU I put on it.

You want to look at the amps on the 12v line. i have a 500 watt allied psu with 20a on the 12v line and its totally inadequate. With that board and processer go big on the 12v line. Enermax makes some good ones with 36a on the 12v line.