May I suggest that you try Audible Illusions M3A tubed pre with external power supply...it's fabulous and a great buy used. Since your amp is only single-ended, buying a pre with balanced in/outs will be redundant. In order for your system to be "balanced" your amp MUST also have balanced connections and connected via xlr's. Higher gain does not necessarily mean better sound.
Hope this helps and good luck with your pre search.