Some of the best pre amps used for $600 or less

You might want to look into the Mapletree Audio linestage, two box, tube regulation, variable gain, and $760 new! Made by hand, point-to-point by a retired Canadian electrical engineering professor and audiophile.

There is allot of Krell stuff that SHOULD BE 600, but people keep overpriceing this stuff. It is great if one can get it cheap enough and when it breaks you don't really need to worry- just get another one if it is cheap enough.

musical fidelity a3cr, hard to find cause they usually sell quick at $600 or under

older CODA linestage

CJ PV10a

Perhaps a Dehavilland? They are underrated and underpriced!

I second the McCormack idea: I think you can get an ALD-1 for around that price. If you want to upgrade later, another $1300 through SMC Audio takes it to a level that few preamps under $10k can match.

good luck with your search!

Forgot to add the Eastern Electric Minimax. I sold mine for $590, and it was a great preamp, sounded awesome in my system.