I just installed 225/45R17 A/S 3's on the rears (215/45/R17 on the fronts). The 225's come in a Y-speed rating, and are actually lower in price than the W-rated 215's on tirerack right now.
I was concerned about the 225's having a taller sidewall than the 215's, but it's barely noticeable, if at all. They're look identical from the side actually (225's on the rear tire, 215 on the front tire).