I just upgraded my system with cheap subs and boy does it sound a lot better

Pioneer 7300 Headunit (Top of line 2 years ago) - $350
Pioneer 6"x8" Speakers (x4) - $150
Pioneer XM Radio Unit - $150
Pioneer 760 Watt Amplifier - $70
Q-Logic 700 Watt 12" Chrome Subs (x2) Mounted in Bandpass Box - $90

Total - $810 (over the past 2 years)

2005 WR Blue Pearl Subaru Impreza WRX STi 2005 Silver Mazda 6s 5-Door ATX Bose Sound, Moonroof, Leather, Clear Tails, Sirius