Bought these sound unheard from an Amazon vendor for $180.00 on the strength of reviews by evaluators I've come to trust. They do require breaking in as do all headphones/loudspeakers, etc. before they begin to sing. I'm more than satisfied with the sound quality not to mention the solid build quality. While many reviewers/owners classify these as "bass-head" phones, I find the audio to be very well balanced across the spectrum with no particular frequency band emphasized over any other. Long listening sessions are comfortable (Most comfortable cans I've owned) and the sound is not fatiguing at all, at least to my ears.
I listen to traditional jazz, fusion, R&B, house, rock via hi-rez downloads, Pandora, MOG, last.fm and ripped CDs (FLAC) on an external HD through a laptop running JR Media Center 17,output to a NuForce uDAC2 and Audioengine2's. My only criticism is the highly microphonic fabric covered cable. That can be compensated for but one should not need to.
For portable listening I have a SanDisk Sanza Clip+ and a NuForce DAC/Amp (out of production) w/16GB Micro-SD cards. My backup phones are Koss Porta-Pros.
Unfortunately, it's damn near impossible to audition a wide range of cans without actually spending money to "buy & try & return" if you don't like. With the M80's I bought, tried, liked and kept. My next upgrade may be a new DAC/Amp (e. g. FiiO E17, iBasso T3) that can serve double duty, desktop and portable.
As always, your mileage may and does vary.