I think Iceteebone was just saying that alot of people that use the gain/bass knobs view them as purely a volume knob, and don't take into account that if turned up to much can send a clipped signal to the sub or speakers, which can ruin them.
However, I find myself using my bass know quite a bit to level out whatever music I am listening to...as most music (especially different radio stations) is recorded at different levels, some with more emphasis on bass, and some with less.
You still need to give a budget though. There are proabably hundreds of amps out there that will do that power. Help us help you.