Pre-amp suggestions for Thiel 2.4/Pass Labs XA30.5

FWIW, some years ago David A. Wilson writing in the Absolute Sound, suggested that a low output impedance DC coupled pre into a low input impedance DC coupled input impedance amp could offer the best Xc factor.

I totally agree with Unsound
I have the Thiel 2.4's and they need lotsa amperes to start to sing .. in fact I dive them with two Parasound JC1's
Forget the ridiculous power of the Pass Labs XA-30.5 .. kinda splendid amp for Harbeth C7ES or Super HL5 but totally useless on the Thiel 2.4.

Have you looked at the Thor ta2000 listed right now? I think he has it at around 2900 but you may be able to get it at close to your budget. I just bought the ta1000 and it is great. Great new owners of Thor to take care of any maintenance or upgrades you may be interested in.

Modwright LS 100 with built-in phono stage would be a possibility. It is a true value, as are all of Dan Wright's designs.

The Atma-sphere MP3 would match up very well with the XA30.5, although it also worked very well single-ended with the Joule LA-150 MKII and Signature edition, both of which can be set to a lower output impedance. If the 2.4 is anything like the 2.3 and 3.6s I think the combination of the rich tones of the Joule would do wonders with a speaker as neutral as the Thiel, a little warmth would not be a bad thing. The combo sounded pretty darn good with my Merlin VSMs which are also not particularly forgiving speakers. You would not have suckage with either the Atma-sphere or Joule preamp mated to your Pass amp.