You have a number of choices in your price bracket, assuming you are looking for a preamp only (not a combo preamp and HT processor). One of the best values on the market is the Adcom GTP-750, which is listed as a "Class A"
component by Stereophile mag, yet has a MSRP of about $1250.
I also have experience with the Bryston BP-25, which has very clean, transparent sound that is grain-free (it also has a 20-year transferrable warranty). With due respect to Megasam, I'd be a little careful about the Marsh preamp. It got a fairly mediocre review in the latest issue of Hi-Fi Plus mag, although the companion Marsh A-400 power amp got very positive comments. Since you are willing to consider used gear, you might also want to search for a recent model Klyne preamp. Stan Klyne builds a superb preamp, and you may be able to find a used model within your budget.