I've been using a SansAmp RBI with no cabinet straight in to the board for most of my gigs. However, I'd like to start using my 4x10 cab with it for some larger rooms. I need a preamp and I know nothing about this stuff. What would work the best? Is their a 1 rack space power amp that would have enough power? I'd love to fit it in my current small rack. Also, currently low on funds so would love not to spend much. Thanks!!