@thosb,:
Thiel CS2.3 Loudspeaker Specifications | Stereophile.com
Thiel CS2.3 Loudspeaker Measurements | Stereophile.com
Thiel's recommended power for the CS 2.3's was between 100 and 400 Watts per channel for an amplifiers standard 8 Ohm rated output. Thiel also suggested a minimum of a 3 Ohm load, how ever as indicated in the 2nd link independent testing demonstrated a 2 Ohm minimum load and with a high capacitive phase angle to boot.
This all suggests that ideally one would have amplification capable of delivering between 400 and 1600 Watts per channel into 2 Ohms, depending of course on one's room and desired volume levels. Be wary of amplifier manufacturers claims of "being stable into 2 Ohms". That only suggests that the amp won't go into oscillation when presented with a 2 Ohm load, not how much power it will actually provide, or how much distortion will occur at 2 Ohms, or how it good or bad it will actually sound into 2 Ohm loads. I think you'll find that theses requirements will make your short list that much shorter.