If you're looking at JBL and infinity for subs and amps I'd say they're alright but not a good choice. I'll go for Zapco, Phoenix Gold or MAYBE Alpine V12s, other than those maybe they're powerful but I'm talking about clean sound (even for bass) not cheezy brands. If you do some research, you'll see JBL and Infinity never get to win IASCA or major competitions but the brands I refer to was well known and well made.
E46, I'm not dissing your system, they might be good but I'm talking about the pure bred sound quality here and I think a lot of people here wants to enjoy their car's sound. Especially he's only talking about a 600 bucks limit on a head unit. Can Clarion make anything with 3 4 volt preout with sub control and can produce 50 x 4 mosfet power? I can tell you that I've seen a Pioneer head that could bridge it's rear channels and power a single 10" (even though it's not recommended). I'll NEVER go to Future Shop for car audio, even MTX is consider "dirty power" these days, and probably you're buying those items from Future Shop. Try go to Auto Sound Design and check out their inventory, you'll know the REAL difference.