Here's my 2 cents (well 1.75 from the conversion rate)
I had some rims&tires from my previous car (15x10 with 265/50's and 15x8 with 245/50's, with 4" backspacing)
The 15x10's fit in the rear okay but the 15x8's did not fit bacause of the calipers in the front. The 15's people here are running are super skinny with weird backspacing (drag rims) so this will not work.
If you must have more sidewall get some 215/60R16's if you want smaller diameter rims, that is what I run in the winter, but trust me these cars do not like small rims and high-sidewalled tires they get angry and drive into poles. At least thats what mine did.