That's exactly the route I went. I valued the moonroof and extra options of the Platinum more than the suspension of the SR. I haven't installed the spoiler yet, it's sitting in my garage and can't wait to do so. Re: the ride difference. I do feel a lot more of the road with the 19's but nothing I'd complain about. I would say I feel less roll in the tires when cornering with the 19's as the walls are lower profile than the 18's. I am riding on BFGoodrich G-force Comp-2 A/S tires.