I can't say that I recommend Head-Fi.org not because they lack information ...they most definitely have it, it is just getting them to share it. I saw so many people asking for help that got ignored it really kind of irritates me, not sure why. They have far more traffic from their regulars (all times of the day even) but they would rather talk about how they got called out for not wearing Beats Audio (200-300 pages worth) than help people.
That aside, I picked up some information in my nonstop daily search for a good pair of quality headphones so I can help ya out there. I'm not extremely knowledeable but I can help give ya ideas on what products to look at. For example if you went the music headphone route, you could get away with spending $180 for nice quality set of cans, $70 if you want a portable amp (for iPods, phones, etc.), and/or $96 for a small desktop amp. You can pay a little extra ...as I did for comfort reasons. Also there are some portable/desktop amp combos for $180. That seems to be the price range for people like us - so roughly $346 for a pair of headphones, portable amp and desktop amp on the low side or $430 on the high side. I will say though, you could easily cut out the desktop amp and still be happy. I currently don't have one and I'm happy. I am waiting till the Fiio E15/E17 releases and then I will make my mind up then. The next step in audio quality is a huge step.
Honestly though, what makes the biggest difference is the type of music you listen to. Not all music gets a huge bonus - sadly rock and classic rock do not ...despite it being most of my favorite type of music. Electronica/Trance and Jazz/Blues probably gets the biggest boost after Classical. So before you spend crazy amounts of dollars, figure out what you'd primarily be listening to. If it's primarily Rock - talking like 80% - 90% - I probably would just buy
Audio-Technica ATH-M50 since you shouldn't need an amp with those even though they would benefit from one.
If mostly Jazz/Classical and just all around good set for everything else - Beyerdynamics DT 880 / Sennheisers (multiple price ranges) and Denon AHD2000 ...but get a amp
If mostly Electronica/Trance and good at everything else - Beyerdynamics DT 990 / Ultrasone Pro 900 ...need amp