You're right. I think I'm going for the Eclipse unit. I pulled the lower climate controls out before and found enough room to move them down and fit the Eclipse unit above. I can make a custom plastic trim panel to cover everything, that's not too hard.
I just want to be sure I can disconnect my OEM stereo without causing any problems to the car? I want to be sure about what the computer is running through the OEM stereo first, or if I need some special connector to make it compatible with BMW.