I didn't go through the whole thread but here are my thoughts when it comes to exotics:
The size of the car is very important for your potential use. Any exotic you will get will be smaller than an M3, so if you're looking for a 4 seater your best bet would be a Porsche. There is also Ferrari 612 and the FF, Aston Martin DB9 with potential to sit 4.
Reliability is another issue you should address. Both Italian and British cars are delicate cars which may become an issue in cold winters and harsh conditions. Having a reliable car and a dealership close by where you live is an important aspect.
Performance, while the M3 is not a slow car, a Turbo or a 458 is on another level of speed. We're talking about cars with 0-60 in less than 3.5 seconds, and the needle keeps on climbing like nothing on the speedo. I'm not going to even discuss handling because on a legal road there is no way of coming close to the max handling of the M3 legally, let alone even a better car.
So here are my thoughts on the subject. If you're looking for something more exotic while being reliable, faster and still maintaining a functionality of fitting four people a Porsche may be more suitable for you