you can get an incredible system for $800 if its not from crutchfield!

ok i have a BOSS 200w head unit with one Type R 12" in a home-made ported box powered by a fusion fp-1402 amp, and fusion 6" in the front. i made the box and did the wiring myself.

i spent

$140 <-----sub
$300 <-----amp
$45 <-----4 gauge wiring kit w/remote wire and RCAs
$100 <-----head unit
$60 <-----front speakers.
--------
$645.00 <-----total

you could get another 12" and it would still be under 800.

if you just want to bump you can afford to leave all the speakers stock....just turn the treble down when you do....i have a friend with two memphis HPO 12"s that registers a 140-ish dB and he didnt spend more than 1k. It can be done, u just gotta look around