Last year when I bought my M3, the final decision came down to two cars. M3 or Cayman S. When buying a pure toy, you really must consider how much you will actually get to drive it. My M3 is also my toy. I have a Cayenne as my DD. Still, I needed the ability to transport my kids and people. Much of my fun driving is interspersed with kid transport (drop kids off at activities/friends house, then take a spirited drive home, etc). I also take my M3 to our vacation home on the coast of Maine. It is a 2.5 hour highway drive. As such, I needed a degree of comfort and cruisability. Finally, even when vacationing, I needed to be able to carry a certain amount of people and "stuff" from time to time. Either that, or I don't get to enjoy my M3 when vacationing on the coast. How sad would that be?!
Remember, the argument that "I have another vehicle for practical stuff" doesn't hold if you spend so much time doing practical stuff that you never get to drive your toy.
I actully love to drive. Having a garage queen doesn't do it for me. Having a pure driving toy is a romantic idea, just make sure your life situations are really such that you will get your drive time.
Audi S6 * Audi S3 * Porsche Cayman GTS
--Former BMW M3 owner