E30 Zone

What is the standard spec of an '89 M3? In terms of ICE, I mean.

I don't want to get too involved in it, but I'd like to run some better speakers off my 4x60W head unit. Ideally I'm just after some direct replacements, no amps, subs etc.

In saying that, how easy would it be to fit some 6x9's in the rear?

If you want 6x9s your gonna have to start chopping the rear deck, the metal underneath the parcel shelf.
Just depends how bothered you are about making it "non standard" as fitting some good speakers are a one way affair!