Kevin in Atlanta

I went with a Becker CDR-220 and changer, had a custom harness built. Looks great. Sounds good. I went back to a six channel amp for the 10 speakers. The PO had put a Kenwood head unit and CD changer, replaced the door speakers(butchered the door and panel), woofer behind the seats(cut into the body to make them fit and, 2 Kenwood amps along with a couple of 12" XPL subwoofers built into a custom enclosure that is gathering dust. I guess I have put that all on Ebay someday.

Jessa

My JVC unit came with its own connector to install in the car. I just cut the old one in the car off (not original wiring, either, no loss) and crimped the new one on. I had to file the sides of the plastic console trim down a little to get the unit to slide in. Fairly simple because, mercifully, JVC and Porsche (or whatever was in there) color codes were close enough that I got it right the first time.

nicobel

You can replace the front 4 speakers with a set of newer component speakers, the little teeters are giving you most of the "directional" sound, along with the other two in the doors.
For the big speakers behind you, i would get a pair with a nice low freq. response, they have a bypass filter to let pass only low frequency, giving you more amplitude.

I think the far rear speakers are mostly to impress? They don't have much effect whatsoever.

928's are really easy to wire, you can install almost anything you want (almost)

my 2 cents...