Good Headphones...What should I Get?...

There are so many on the market, it will depend on how much moneyyouo have to spend, what headphone amplifier you will use, and what style you like (around the ear, in the ear, on the ear). I recommend that you check out the following websites for more information:

http://www.headfi.com/
http://www.headwize.com/
http://www.headphone.com/
http://www.goodcans.com/

Some are commercial and sell products, including their own, and others are forums.

I own the Sennheiser 600, an Antique Sound Lab amp, and nice cables. I like around the ear phones for longer listening. The Senns are detailed without being fatiguing. The ASL amp is tube and to my ears is very melodic. Once you have done some investigating, come back. I'm sure the folks here will be quite helpful. Happy hunting!

Hmmm .. you remove room resonances for sure, but you also destroy the spatial information ... the music all ends up in your head.

I use headphones when I must be quiet, but otherwise I always listen with speakers.

For the $500+ that you'd spend on good cans and an amp I'd take this money and improve my main rig if I were in your position.

Of course, the headphones would not replace my main rig. The idea is to use them as a reference in regards to the source material played. Short of a dedicated listening room, I think acoustically I've done all I could to my listening area - I've learned to live with and enjoy the imperfections of my environment.