I'm trying to decide what to do with my car wheel and tire-wise, there seem to be options whether you go with 15s, 16s, or 17s. I think my next set will be 17s with 225/50 fronts and 255/40 rears because I want the extra width (as well as tire flexibility). If I were trying to do 15s I would definitely go with a 205/50 front and 225/45 RS-3 and deal with the fact that they are nearly an inch shorter in radius because they are very good tires, and anything larger in diameter seems to be impossible to come by in a proper tire.
It seems this community often overlooks the fact that there are certain sizes in tires that offer street tires that are heads and shoulders above the avg. street (or even 'performance') tire; basically sizes marketed to autocrossers and track people. One of the greatest upgrades can be going from a normal tire to one of the latest autox tires, totally changes the limits(/fun) of the car.
I like this calc as a quick reference for tire sizes:
Tire size calculator
Also, I think it is misleading to say "x" aspect ratio tire is floaty or softer because it's a function of the width of the tire.