I never thought I'd say this, but headphone amps make a big difference. My whole experience has been with amps that are under $500, but I was at a friend's house this weekend and he's a DJ. He has a number of amps, but the one he likes the most is the HeadRoom Home Balanced Amp. I had my Etymotics in the car, so I got a chance to try them out (albeit with adapters) on a much higher-end amp. I must say, I heard more detail than I ever heard before and it sounded fuller, too, w/o loosing the detail, which for me is a big plus. Even my the MP3s in my own player sounded better, although the best result were from the turntables.

Now I'm not about to spend $3K on a headphone amp anytime soon (for him it's a tax-write off), but it was quite intriguing to find this out.