Best used amp for < $500?

Electron Kinetics Eagle 2. If you see one, jump on it. Vastly superior to NAD and Adcom. The on/off switch is notorious for going out, but can be replaced. Will drive a .5 ohm load all day long. Designed and built by the (late?) John Iverson.

Oops! Sorry about the double post!

The PSE Studio IV is the best amp I know for under $500 used. It matches the Eagle 2C (also excellent) in bass when driving 4 to 8 ohms and is sweeter and smoother overall. I have not heard the Belles 150A. I would love to hear from anyone who has AB'd the PSE against the Belles.

Vdotman and Jazzzman are absolutely right about the Eagle and PSE. They are lightyears ahead of any other 2-channel amp selling used under $500. I have heard most amps from Adcom, NAD, B&K, Parasound and the like - they don't come close in terms of refinement. The Belles has promise. But it uses MOSFETs so beware the bass.

Linn LK-85 is my recommendation. For 400+ you CANNOT find more musical amp, that will satisfy all your listening needs. From classical to rock.