Very good points, Weargle, and my only comment is that the "width vs stiffness" debate rages constantly over on the SCCA forums. "Should I run 205 or 225?" "Will the 225's heat up enough during a run?" etc.
Also, when I said 16 or 17, I guess my point was "Don't slap 18's or 19's on your car." I agree that the best, most hardcore choice would be to run 15's with low-pro tires, but for those of us actually using our tires on the street, I'd rather recommend a size that lets us keep our final drive ratio intact. So, plus size but light weight wheels with low-pro tires, etc.
And of course, budget is a player. "...that you can afford" should be a standard caveat. But you can see from the pictures you linked to what a difference .5" makes.
