Thanks for your inputs so far... I realize that if I were buying an amp particularly for the TH-900 ( as I actually did for my Sennheiser HD-800s (the HDVD 800), my Grado HP1000s (the Grado HPA-1), and my Grado RS-1is (the Grado RA-1), I would get something mentioned on this thread, perhaps one of the Fostex amps.
But I am trying to perform "due diligence" before purchasing a TH-900 that one of the amps I have already will not limit the TH-900's performance... I can't afford to get another amp just now (actually, can't afford a TH-900 either, but, well, you know...)
Thanks!