i would suggest DIY
its really simple if you use the guides on here...
ive never installed audio systems and did my e90 wiring harness and JL amp in 4 hours proper and clean.
if you want a hand with anything, im downtown and can help
first:
http://www.e90post.com/forums/showthread.php?t=641323
pick which setup you want, what stereo do you have now? what is your budget?