Harmon Kardon isn't that great tbh, a bonus if you've got it but I wouldn't consider retro fitting it, power fold mirrors are definitely an option I wish I had in my coupe.
Finding replacements wont be cheap but keep your eye out on ebay for a genuine facelift set, fortunately all facelifts have ribbon type wiring so you just need the switch no.61316901383 then its just p&p.
I got the above info from Pictorial DIY Guide: Retrofit Power Folding Mirrors to your E46 BMW (1997 to 2006)! , I'd bookmark it if you're thinking of retrofitting a set?
Unfortunately I'm not sure if facelift M3 mirrors work or not!