An interesting post in this thread:
I have the Sasha 2 powered by the ARC Reference 75 SE which is more than adequate. Prior to my purchase I did a fair amount of research, and on two sites it was reported that Wilson used the Ref 75 to voice the Sasha 2 s.
My dealer had the Sashas setup in the showroom with the Ref 75 SE for demo purposes and he knows his stuff owning the same store since 1977. He did hook them up with the Ayre mono blocks which also sounded quite good ( a lot more money ), but to my ears I preferred the ARC.
My listening room is 21x15.
There are presently three used Audio Research Ref 75 (non-SE) power amplifiers listed for sale here, for less than $5K, and for less than $4K in one of those cases. Note though that the ARC Reference series amps provide only balanced inputs, and will not work properly if provided with single-ended inputs via RCA-to-XLR adapters.
Regarding phono stages, personally I would not let the inclusion of a phono stage be a factor in selection of a preamp or integrated amp. It would most likely be best to add a separate phono stage at a later date, such as the superlative Herron that was mentioned.
Good luck. Regards,