I was in a similar "predicament". I have owned an M6 for the last 6 years, and just sold it last month. so I went on a hunt and drove everything in the price range. Heres my 2 cents:
1. R8-Absolutely an eyecatcher- but have you driven it? "auto" transmission reminds me of the SMG I just sold. Manual would be better. Minimal luggage room. I dont know if taking a weekend trip in your new car is w priority, but there is only a small area in hood that can accept a gym bags worth of luggage. Doesnt work for me unless you plan on driving mostly around town. AWD is a nice touch
2. Maserati GT- Another beautiful car, a bit underpowered. Its mor about the "luxury and class" of a maserati than fun to drive. Expensive maintenance. Beautiful interior. The MC version is the one I would choose.
3. Porsche- Panamera or carrera- Great driving cars, beatiful classy styling. Alot of fun to drive. High on the list. ALOT of these in SoCal.
4. Jaguar XKR-S. $132,000 sticker. 550 HP. Light and fast, beautiful styling, 100 built a year. Old NAV and electronics systems (no traffic on Nav). Handling not as good as BMW or Porsche. Maintenance included
5. M5/M6- just love the combo of handling and power. Maybe because I have had a BMW for so many years, it just fits and handles great. What I am leaning towards. M6 is on order and will be here by end of month
6.Anything from MBZ- just dont like the electronic steering and driver inputs.
Otherwise very luxurious fast rides. CL63, C63 black edition, E63 are what I drove.
I may have missed some but my advice is to drive em all at least several times and if possible in succession. Nice way to spend a weekend.