I'm suprised no one has mentioned the Audio Research D-130. This continues to be IMHO the best buy for AR on the used market. Released in 1996 and only replaced last year with the 100.2. Available for around 1 K or less. I have one matched with a Audio Research LS-3. The combination is wonderful. I do believe that these solid state amps have a synergy with Audio Research preamps. I do not think they reach their potential with OEM preamps.
Audio Research Convert...
I never thought I would do this but I've recently sold my Ayre V3 for an Audio Research 100.2, I have two words to say about it. Dynamic and Smooth! The 100.2 has all the qualitys of the Ayre, but even better resolution on the top and the bottom, and so smooth. There is just such a sence of ease with this amp. I believe part of this is that it is also a better match for my Audible Illusions M3A. This amp is a real sleeper and it really takes charge of my Maggies. If anyone else out there has this amp I would love to here the contents of your systems.