Krell, Audio Research, Mark Levenson, VTL, BAT, Cary just to name a few of the more popular High End amp companies. Though most make some amps in the "affordable" 4 to 8 thousand dollars range, thier really high end stuff will be in the 10 thousand dollars or more range.
Tenor, Lamm, Sim Audio, Edge, Nagra, Electrocompaniet, Orpheus and Thor Audio all make great amps. In fact I plan to buy a pair of Thor Audio TPA-30's later this year.
The above - or an enormous number of much cheaper (and more expensvie also) amps, both standalone and in receivers. I can't list them all because I just ain't got the time or the inclination.
To put it simply - if the amp in question has a high input impedance, a low output impedance, has sufficiently low noise and distortion, is stable into the load and isn't overdriven, then, bucko, it's as good as any other amp at any price.
McCormack; especially the DNA Deluxe series. The same units, after being upgraded to "Gold" or "A" status by Steve McCormack (smcaudio.com) are reportedly some of the best-sounding solid state amps available for under 10K...