Spend a bit of time e-mailing & forum trolling regarding the new BMW M5, and found that there are a lot of significant first year glitches to deal with, so I'm going to wait and check back in a year or so. Which means that the Maserati gets to stay!
Looked at the 645/650/M6. The rear seat in the M6 is perceptibly smaller than the rear seat in the Maser Coupe. I wasn't fond of the carbon roof either. Plus, the M6 will share the same first year blues as the M5 in the areas of drivetrain and electronics. If I go with an "M", I'll wait until the manual trannies are shipping in 2006 and all of the bugs have been worked out.