Nimble,
I like the idea of stepping up to 17" wheels, but be prepared to pay a premium price...
Also, 56mm (2.2") positive offset on a 17x9 wheel equates to 6.7" of backspace, very possibly too much for your application (in my estimation) without resorting to thicker spacers in the back along with longer wheels studs.
Good luck, whichever way you decide to go.
Mike
