Bryan,
I really like the AES DJH preamp, which you can get used for around $1000, usually less without the remote. It uses 6SN7 tubes, which many believe to be "tone monsters". There are lots of superb used/NOS tubes around, and several current production that are quite good. Some of the NOS are getting extremely expensive Tung Sol roundplates leading the way), but there are some great tubes that are inexpensive (6SN7GT RCA greyglass, some Sylvania, Raytheon, CBS/Hytron) and some that are reasonable. fun to tube-roll. I've heard that the 12SN7 is also a great tube, much cheaper and some are reportedly as good or better than the good 6SN7's. It's much less commonly used than the 6SN7, a little searching would probably get you some candidates. The only one I know of for sure is the Space-Tech QA-001, which uses either 12SN7 or 6SN7, sells for $399, and is reported to be a great pre-amp...
I also have experienced the Eastern Electric Minimax pre, but have found I prefer the sound of bigger tube octals (like the 6SN7) rather than the 9 pin 12AU7.