I had the same problem with my Jeep TJ. It had great sound a year ago, then it started sounding crappy after the M2s arrived.

Oddly enough, the stock sound system in the Magnum (not the Boston Acoustics upgrade that made the Hemi too ^%#$%^ expensive) sounds great even if I go straight from the Axioms to the car.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8