Square tire setup on staggered rims?

threeseventy

You want responsiveness in AutoX (and all tracking) and while wider is generally better, putting rear-appropriate tire sizes on the front won't allow for the slight stretch that gives you that responsiveness. The moment of inertia will be higher as the sidewall waits to stretch and react each time you turn. To maximize grip go with the sticky RS3's @265 front 285 rear since you have that much whp.