Our generation Sienna had both 16" & 17" wheel options, so question one is what size snow tires did you order? IIRC, the larger wheels have wider tires (215 vs 225), and thus a slightly different offset to compensate and keep the same centerline. So when you go shopping for other Toyota wheels, you need some specs. Weight carrying? Opinion... but I doubt there is a substantial difference structurally between an OEM wheel made for a 3800 lb car vs a 4400 lb minivan. 600 lbs distributed between 4 corners isn't much of a delta.