I had the A3CR and Thiel 3.6's. I had upgraded from a McCormack DNA-1 amp- it was definitely a step up in terms of high end extension, delicacy, detail, etc. On the other hand, it was listed as 150w by Audio Advisor but was really closer to 120W into 8 ohms (a step down from the 175w of the DNA-1).
I have since upgraded to Classe CAM200 monoblocks, and there is no comparison- great improvements in bass extension, control, pitch, and ability to go much louder without strain or compression. I think part of the secret is that the Classe doubles its output into 4 ohms, while many other amps don't come near to doubling.
Admittedly there is a fair price difference between the two amps, but I finally found a way to make the 3.6's 'sing' with a bigger amp. The A3CR is a bargain for what it costs, but just won't be near the ultimate for Thiels' demanding load.
Best of luck in your search.