These Thiel’s need an amp with grunt to sound their best, lots of current, that really means Tubes or Mosfets are not ideal. Amps that can almost double their wattage from 8ohm to 4ohm to 2ohms, would do the right thing by them.
From the Stereophile test results.
" I actually found the minimum impedance to be 2.4 ohms at 125Hz. The difference between 2.8 and 2.4 ohms is academic, either mandating use of an amplifier that has no problem delivering high currents"
http://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements#POtrL7hdCUOxjofF.97
Cheers George