Front-End to Add to Amplifier?

I've made a pragmatic amplifier move (Kustom Groove 310C combo), and am looking for a preamp of some kind to run as a front end, either to the fx return or straight at the input. Don't know what it'll be yet though I've got a couple ideas.

Simpler is better than feature-rich, I'd like it to fit in a cable bag. So far I'm considering:
SansAmp VTDI,
One of those Ehx Bass Metaphors things,
Something with eq, like the SansAmp Q-Strip...

Something with a midrange sweep could be of interest.

Cheap is, as always, desirable. Thanks for your time...