I thought you mentioned in a thread that your car "never" sees rain and is basically a garage queen already?
Anyway, I've had the pleasure of owning a couple of exotics and I have to agree with most of your post here. Cost of maintenance is ridiculous. You have to replace belts every 3-4 yrs (I think 5 yrs now) and the cost of that is $4-5K and that's for an engine "in" belt service (360, 430, 458 etc.).
Engine out, such as a Testarossa, will run you in the $8-10K range every 3-4 yrs. and this doesn't include other parts that "may" need replacing during that time (clutch, etc. depending on the how frequently you drive and how hard you drive it), which is even more $$$
These cars are generally garage queens but I know of some F-car club members who DD their cars rain or shine AND even in the snow!
The M3 is everything you mentioned in your post.
It attracts attention - but not too much
It's practical for getting the kids around going to the store etc.
It's fast (it can be made faster with supercharging etc.)
There is also a new Ferrari called the FF. This car does have back seats for small kids (they say you can fit adults back there, I dunno) and is apparently a "practical" car. Large boot, 4 seats, awd.....
At the end of the day, Exotics aren't for everyone, even if you can afford it.
I'm already looking into the '13 SRT Viper (for a weekend toy and keeping my M3). It doesn't have the maintenance costs of an f-car or Lambo but has the exotic look of one and with 640HP and 600 Lb\Ft, this car is no joke. Plus, I've owned a Viper before and it's just as an emotional experience as an F-car IMO...