I would order forged wheels 20x9 front and 20x10.5 rear which is R OEM sizing and keep the weight down to a minimum. Going wider has no performance benefits and only produces more rocks and debris being thrown at your quarter panels. That's just my .02...

 

About 3 years ago I just followed what another fellow had done with his and put on the following in flow forged (Vorsteiner):
Front: 21x9 +32 (265/30R21 Michelin Pilot Sport 4S)
Rear: 21x10.5 +25 (305/25R21 Michelin Pilot Sport 4S)

Compared to the OEM 19'2 with P zeros the handling improvement was insanely good, it is like a different car. You notice it in particular in fast direction changes, the car really feels much lighter (eg coming out of a roundabout and immediately hitting a tight turn the other direction). The ride was pretty much the same, maybe a touch more jittery on a bad road in dynamic. The best money I've spent on a car, I reckon. I'm getting a Mustang next week, I've already ordered the forged wheels for it with the same rubber.

I wouldnt want them any wider at the front as they almost sit proud of the guard (but dont). The rears could maybe be another half an inch wider.