Just to clarify again, his issue is not power at all. In order to control feedback on an ABG, he has turned down the preamp on his instrument almost completely. As a result, the very low level signal going into his amp is not capable of driving the power section of the amp to anywhere near full output. As was mentioned by a few others (and myself earlier), this is a pure EQ issue period (i.e., feedback control of a wonky ABG). Once he fixes his feedback issue by either learning a bit more about the EQ on his current amp, or getting a 'DB oriented' external EQ with a narrow band notch type filter, he can turn up again and all will be well.
I would again suggest that all who are talking about 'power' go back and read the initial post. The only thing that will happen for the OP if he gets an amp with more power is... well.... nothing.
True! Got off on that tangent. Peace yall!