Sennheiser HD595. Volume is OK. No bass. Good midrange. Verdict - only for voice control...

I use Sennheiser HD-600 and Sony MDR7506.

HD-600 has neutral bass.
MDR7506 plays loud and has more low end.

Sennheiser HD-25 - it's the industry standard in professional sound reinforcement & the UFX headphone amp has more than enough juice to drive them.

I too uses the Sennheiser HD600, great headphones.

I just picked up a pair of "VMODA" LP2's based off a very large headphone roundup/review, and not being satisfied with my growing selection.  Holy crap - These things have some serious low-end and are very sensitive!  Even with their present bass, they still image well and have less than 2dB tolerance from pair-to-pair.  Built like a Tank with military specs!!!  Kicks the 7506's in the behind w/o breaking a sweat!!! (but also 2x as much for $199/pr).

http://v-moda.com/crossfade-lp2-limited … tte-black/

The V-MODA LP2's are my new favorites from my selection of MDR-7506, MDR-7509, DT770M, Shure SCL-5 IEM's, HN-7506 Isolation Cans, and a few others I can't recall...

Been meaning to audition the HD600/HD650's, too - but I really need closed back cans to justify their purchase (for tracking flexibility).

FWIW - The Dr Dre "Beats" headphones got miserable reviews on the roundup/review I referred to - No suprise there, huh :-)  If you are interested, Tyll Hersten's headphone roundup is summarized here as a Podcast (Home Theater Geeks w/Scott Wilkinson):
http://www.innerfidelity.com/content/to … ks-podcast

This guy knows his cans!!! 

Ahh... What a Sound... Very detailed and natural, also a very good stereo imaging.
Great for me...

Fireface UFX to Ultrasone Signature Pro woithout an external Headphone Amp.

I can hear every compression in all of my Songs. (mp3 compression too)