I don't know about the wheels but depending on what you do to the car consider the following;
I run 235/45/17 on all four. My car is lowered with TEIN flex and even running max stiff damper with semi-stiff pre-load I still bottom out in the front wheel wells under heavy breaking/cornering.
My conclusion (so far and may not be correct) is to run 245/40/17 front (lower profile, a little wider, but not 18") more rubber on the road but lower profile to help eliminate wheel well rub.
I will go 245/40/18 in back as there is more room in rear wells and I hope to get a little more needed grip back there. May even go up to a 255 width in back.
If you don't lower your car, don't race or drive hard maybe 18" in front will be fine.