Threshold to Pass upgrade?

I have not heard the Threshold amps, but did own the XA100.5 (see my review) and now have the XA160.5. I would guess that the supersymmetry of the later Pass amps would contribute greatly to lowering the noise and lessening distortion for a more clean, transparent and dynamic sound. I also own the XP-20 and Xono and can tell you they make for a great combination with the XA.5 amps. Can you hear the XA100.5 in your system to compare?

Pass will be better, but not $10,000 better. But if you have the money, audio is my favorite hobby to spend it on. :-)

Lots of good amps in that range, and I would first make sure you are happy with/keeping your speakers and then find the perfect match for your final speaker selection.

If you like your Threshold and you're looking for an interim solution(doesn't sound like you are), you may have Jon Soderberg upgrade your T400.

http://www.vintageamprepair.net/

Thanks for the information from everybody so far. Very helpful. Has anybody heard an upgraded T400? I'm quite curious about this option as well - I definitely find the Class A sound very attractive and would like to keep those qualities if possible. Yes I know I could spend $$ and upgrade to the XA100.5 too....