http://www.e90post.com/forums/showthread.php?t=641323
BMW stereo types
http://www.e90post.com/forums/showthread.php?t=352586
http://www.e90post.com/forums/attach...2&d=1266451970
http://www.e90post.com/forums/attach...2&d=1260829447
http://www.e90post.com/forums/showthread.php?t=343673
http://www.e90post.com/forums/showthread.php?t=138949
http://www.e90post.com/forums/attach...2&d=1260829447
http://www.e90post.com/forums/attach...1&d=1209780605
http://www.e90post.com/forums/attach...1&d=1209780865
http://www.google.com/url?sa=t&rct=j...QNFyu70IsyKRlg
http://www.musicarnw.com/page-2/
http://www.e90post.com/forums/attach...4&d=1278871872
head unit
http://www.e90post.com/forums/showth...hlight=dynavin
http://www.e90post.com/forums/showth...hlight=dynavin
http://www.e90post.com/forums/showth...hlight=dynavin
http://www.e90post.com/forums/showth...hlight=dynavin
If everything is already ripped out you might as well stay with aftermarket . The BMW systems have no real crossovers. ( I think they may have an inline cap on the tweeter line) If you have aftermarket speaker use whatever crossover comes with them.
If you ever have to have programming done or software values changed in the car you will need the original head unit installed for the BMW repair computer to work with the car .
You may be able to bypass this with a coding setup.
(But BMW won't.)
When you say under the trunk floor typically the TCU telephone control unit is under the floor in the center and satellite radio i believe. The amps are in the rear drivers side corner in the US next to the taillight assembly .
If you have questions post more pictures that aren't such close ups. The large black connector with the lever is the amp connector the fiber optic lines are in one of the others .