Just a suggestion if you don't mind it being more that 1u..I'm about to take the plunge on making a preamp separately by getting a rack eq and limiter, using a DI to get a balanced sound and using the eq as gain essentially.
You go from the DI into the eq, then into the limiter and from there into the power amp..it also doubles up as a guitar rig too if you have a guitar cab handy
I've been looking at pre-amps for a long time and never found one that has the right balance of price/quality that was on the market at the time.
Good luck in your search!