Thiel 3.6, what will drive them best?

I agree with B&K M-200 mono blocks. The best high power amp available for <$800. Some can be found for $500 or less if they're the early vintage (which perform as well as anything). Current galore!

Tvad, interesting reviews that I haven't seen previously. One comment I find curious

aging B&K M200 mono amplifiers, rated at 200 watts each but certainly not current powerhouses.

. B&K rates them as 150 amps peak-peak, which is the basis for my statement. The biggest challenge I've presented them is Totem Mani-2s, which they drive very nicely, and I've no other basis for supporting refuting the rating. I don't presume B&K's rating is necessarily accurate, but it's has me wondering what the reviewer's baseline is causing him to make this statement.

Another amp worth considering in this price range is the Parasound HCA2200. Either the mkI or mkII can be found used in the $600-800 range. I have the mkI which I liked a lot, though I replaced it with a pair of M200's which I preferred. I think the differences are in the personal preference range and some my like the HCA2200 just as well as or better.

What qualities made you prefer the M200's over the HCA2200?

It was multiple factors. Sonically, both are excellent, but I thought the M200s were a little more neutral and warmer. The HCA2200 runs hot, indeed generates a good deal of heat which in the summer was an issue in my room. The M200s can put out heat too, but not as much. Finally, I prefer mono blocks for placement purposes, in most situations.