Polk EX3550 5.25" components
Just bought them from Crutchfield (because they are no longer made and I got them super cheap) Installed in a BMW 325i convertible (1987) and they are quite impressive.
Most of the BMW audio guys agree that the stock speakers (although they don't look like much) are actually pretty hard to beat. The polks are nice units, and the crossovers have pop-off lids for easy access to modify if you are the soldering type. My only complaint is that the speaker wire included was really pathetic. It was really heavily insulated, very small guage wire, and it was cheap and stiff. Fortunately I always keep a steady supply of 12 ga monster on hand :)