From what I know, Thiels are tough on amps. Thresholds don't have a ton of power and really aren't happy below 4 ohms. If you push things really hard, both amps may have issues. The difference between 60 and 100 watts is only about 2db. I'd look at something with a lot more power and lower impedance ratings...just my 2 cents.
Threshold SA3 or T200 amp
I've searched the archives and can't find a direct answer to which one of these amps would sound better with my Thiel CS6 speakers. If the price were about the same, which amp would you buy? They're both class A (60WPC for the SA3 vs. 100WPC for the T200)