I have been prowling the boards for a couple of months for a used pre. I'm leaning towards a Threshold Fet 9 or ARC LS-3. Those are good pres and moderately priced used.
You right about buying used. I wouldn't lose much if it didn't work out.
How about borrowing a preamp and trying the system out, or buying a well-rated used pre at whatever price level you select so you can sell it easily if you dont care for the system?