Let me add to the up-graded speaker topic.

The BSW mid-ranges that go in the dash do not fit without modification. The screw holes in the mounting flange do not line up with the holes in the dash. Not that close, actually.

You have to turn the holes in the speakers into slots. This is easy using a wire cutter to clip a slot from the hole to the outside of the flange. This is certainly better than using a file or tool that would create metal filings, what with the magnet and all.

The directions for the tweeter, on BSW's site, show the use of the glue gun to mount the tweeter into the BMW tweeter holder. The BSWs I got just slid right into the original little retainer clips perfectly, so no need to glue.

Inspect the assy carefully before you remove the OEM tweeter from the holder so that you don't break the retaining clips.

I got my Alpine 6.75s from Crutchfield. They include the Alpine adapters and a set of their own. I didn't see the Crutchfield ones, packed in a hidden place, so I assumed the Alpine units were them and attached the speakers that way. Simply run the speaker mounting screws right into the plastic adapter. Later, when I found the Crutchfield adapters, it is clear they would be nicer, more OEM-like. Someday I will swap them just...because.

BMW's wire plugs are, of course, not compatible with random aftermart speakers, so you have to cut and splice. Not at all hard, but plan on solder and shrink tube or get some small butt connectors.

The hard part is: which wires are positive and which are negative. The speakers came with big and small spade connectors, and they only fit one way, so you have to get that right. There seems to be no info anywhere handy on which wire is which, so here is what I found: If you hold the OEM speaker with the terminals down and facing you, the one on the right is positive. Then, you can see which wire is positive and hook it up correctly.

As it turned out, on my 05 X5, the wires with white in them are positive, at least on the front doors.

Crutchfield offers rubber (?) cups that fit behind the speakers. They serve as enclosures and to keep water away from the speaker. I didn't order them because I assumed the space was so limited. But, there seems to be plenty of room, so I may order a pair and experiment. Heck, I can get the door panel off so fast now that it is easy!

I am interested in how the attempts at cutting a hole in the sub's access hatch and covering it with material works out. If it doesn't, maybe just covering the hole with a speaker grill would work. It could be painted to match the carpet. Lots of cars have visible sub grills now, so most people would just assume it was stock.