I don't see the point of having large wheels and super-low profile tires on a street car. I'd rather not have to slow down for rough roads or be afraid I'll wreck the wheels because I tapped the curb. You can still get better handling, responsive steering, and overall grip of a lower profile by switching to a higher performance tire. I've been testing my theory on my Saturn with 185-65HR-14 BFG Traction T/As. So far they've been phenomenal. To put it simply, I have not found the limit of these tires in cornering yet, and they were still much cheaper than if I had +1 or +2. Plus the ride is still pretty good. A little rougher with a stiffer sidewall, but not like if I had LESS sidewall.
My Mazda 6 came with 16" steel wheels (205/60/16 tires). Though I'm going to switch out to alloys at some point soon, I'm most likely going to stick with 16's. Most of them came from the factory with 17" alloys. I test drove that combination, and didn't see much difference (other than the tires just sliding at the limit, no squeal). I think a 50 series tire is the absolute limit for the street based on the ride, how they handled rough roads, and the likelihood of damage. What I find interesting is a few members of the mazda6club forums have downsized to 16's, but went with a 7.5" or 8" wide wheel and 225 to 245 wide tires and have reported all around better grip and acceleration than with 17" or 18" wheels.