My wonderful wife arrived in my life with a BMW Z3. While it "only" has the base 2.5 L straight six, I find it a great car to drive, although I know it doesn't handle nearly as well as the newer Z4. The 2.5 L still gives a great power to weight ratio.

Paint Protection: We first put on the factory bra and, as expected, it scuffed up the paint. Then we had installed 12 mm clear plastic adhered to the frontend, mirrors, and top of the rear bumper (for luggage scratches). While the idea of a thicker plastic to better bounce off road debris sounded good, this looked really rippley and had very distinct edges. It also shrunk and left a slight mark next to the edge, not to mention a think cut from the razor blade of the insaller. You could see it from a mile away. (Recommendation, stay away from Autobella in Portland, OR)

After being hit on the passenger side of the car, we had a new, much thinner plastic installed from Paint Impact Technologies in Santa Rosa, CA (but other shops should be able to install their product). It is still thick enough to protect the paint from chips and it is so nearly invisible that one has to get down and look just right to see it or the edge of the plastic. It cost about the same as the thick ugly stuff and was installed by someone who knew what they were doing. They even covere up the razor blade mark from the previous installation. Highly recommended.

Stereo: Put in an Alpine retractable head unit.  When the car is turned off, the only thing visible is a blank faceplate, a nice security feature for a convertible. Factory speakers sound horrible.  Someday will put in Focal speakers.

Brakes: I installed low-dust Akebono ceramic brake pads (Front part # ACT558, Rear Part # ACT396). These are the Post Cured And Heat Scorched type. Bought them from Auto Parts Warehouse. I have found them to have noticeably increased stopping power, substantially better brake pedal feel, zero dust, and are definitely better than stock or the previous low dust brakes (unknown brand). Highly recommended. You will be able to tell the increased stopping power. By the way, the brake pads were one of the easiest brake pad installation I have done (and, no, I'm not admitting how many decades I've been tinkering with cars!).

Links: The most avid BMW enthusiast I know highly recommends the Road Fly chat site.