In reply to:
The sub section volume is all the way up, with the bass boost up about 1/3 of what is available.
Hmm. OK, I would start here - can you turn up the gain on the empeg, and turn down the gain on everything *except* the sub?
I suspect you are not hitting the power limit of the amp yet.
In reply to:
Also, i am moving to a bigger car (either a RAV4 or a CRV) and I want to maintain the sound levels. Will they drop significantly in a bigger car?
A car is pretty much an enclosed box, so sound levels won't be affected that much.
Convertibles/roadsters are another matter... And so are land rovers (think "sieve" rather than "box":))