[Amarphael]

I did actually. setup for comparison was: PC>Squeezebox Classic>CIaudio VDA-2>Objective2>HP's.  Musical material was some orechstral and electronic music.
 
Don't bother with the DT990, I've heard them both at 250 and 600 ohms, the latter was the version on comparison. Really, T90 is much more refined, evolved and just moar bettah. It makes the the DT990 sounds like a borderline grainy mess. I should note the DT990 was just new in box at the time so if you believe in "burn-in" take it with a grain of salt.

 

[Allucid]

I found the t90 to sound 'fake' on drums and snares in comparison to the D880 250ohm Premium, and my 880 has some sort of synergy that's addictive that the t90 doesn't. Plus, it's double the price.
I ran the A/B from a A&K100 with a $750 tube amp. Honestly you should either get the T1 which sound great out of anything, or get the 880 at $350 and get a Schiit amp to drive them fully, because by the time you're done getting the best sound out of the T90, you'll be spending up to 1.3-1.5k, which is where the T1 comes in.