Scoring on Used Thiels here

http://www.psaudio.com/bhk-signature-250-amplifier/

Unsound ... you are right the Thiel equalizer has a high input impedance ... either the 90k you mention or perhaps 100k.  That is why it can take the high output impedance of the SP6's or other pure tube preamps.  However, its output impedance is very low, so it works well into the 10K input impedance of the Outlaw monoblocks, which is low even for solid state amplifiers.

There are a pr of Thiel 2’s on local Craigslist , look good , wants 250$, is that a good deal ?