I would not put Fosgate amps in a BMW, I'd go with Helix or Audison dsp amps...
Those 10 speakers are gonna have very low power handling. My Lexus has the fancy pants stock system. With 9 speakers total. And it sounded pretty good for a stock system. Until all of the speakers started disintegrating. LolYes, people are adding additional power delivery for their after-market amps. thanks for mentioning that point.
Example picture.
Yes, I do have replacement subs for the "butthole blasters" already, though from what I've gathered, the biggest issue with these stock Stereo is the lack of power being provided to them. 190 watts doesn't seem a lot for 10 speakers. I read that even swapping out the AMP for a better-suited one improves the system drastically.