Without a doubt...a used VTL 7.5!
Read the reviews in TAS and Stereophile, and search AA. As tube pre-amps go, this is up there, if not THE BEST. I have seen these on AudiogoN in the price range you want to spend.
Another option is a used ARC Ref 2, which I own, but I would upgrade to the VTL in a heartbeat if I could afford to.