I ran a PS Audio S300 with my RP-1 for several years and was very happy, find those for around $1K. Then I found a Quad Artera Stereo for $1.5K and moved to that and also happy. Bryston 3B SST over on USAM in your price range that might be a good match, need to check the specs of course as others have suggested figure out more requirements.
One tweak with the RP-1 that also yielded positive results was moving to a set of Mullard tubes.