Hi,
I also own the Teac and the T1 (1st gen).
While the Teac can drive it to sufficient level (sometimes you need to turn the volume quite high), I feel that it struggles to give size and dynamics to the sound.
The Teac is very good with other cans I own, such as Philips fidelio X2, AKG K550 and Beyer DT880, but with the T1 I don't think it's the best pairing.
Now I also own a tube amp (Icon audio hp8 mkII) which is much much easier with the T1, delivering much more power for its 600 ohms, and making it sing a lot more. I have really discovered the skills of the T1 with this amp.
So, always a matter of headphones / amp synergy...
hope this helps.