17s all around or 18s in back

It seems like you've done your homework. I'd go with the 17" wheels all around. Your tire sizes are definitely safe choices.

The 245/45R18 tires are about 26.7" tall. So, unless you jack up the rear or have larger tubs, I'm pretty sure you'll get some rub at the top of the wheel well. Especially where that little indent is.

If you get Streeters, I think the ones with the black centers will look the best on your car.

http://motechperformance.com/product/17-black-streeter/