To the guys trying to use amps to equalize their T1s: Why not just EQ them instead? Find the frequency that's bothering you and turn it down a bit. If you can't fix them with EQing, you might want to go to a meet and listen to another pair of T1s. You might be as surprised as I was.
Interesting question - using different amps to achieve a different sound is basically EQing with hardware, I can see that, but with tube amps, there's the phenomenon of 'tube sound' beyond the simple alteration of frequency response. Whole thread on this... http://www.head-fi.org/t/721500/how-is-tube-sound-even-audible-in-modern-headphone-amps