I concur with Schubert. The EE Minimax posted here on Agon is a no brainer for $600. I had a TAD Signature 150 preamp which is also a great preamp for its price point. I sold my mint unit several years back for $675 if I recall correctly. There's one currently posted on Agon but at $925 its over priced. The EE preamp is a great choice. Worse case you try it and flip it for close to the same price if you are not satisfied with it.
Good luck
Good luck