I got 325i and there is just 1 amplifier in the back with built in crossover.
2 things, first, is yours a dsp model?
second, how crappy is crappy? do you have something to handle the low's? im getting sub's, so the speakers only will need to handle the high's. maybe this will be do-able, at least for the time being?
No I do not have dsp.
For subs I have 2 sundown SA-10's on saz2500. It's more of a SPL set up.
As of speakers, I will be putting in set of DD i the front and alpine in the back( temporary) and set of sundown neo 8's in the back doors, powered by sundown sax100.4