I just drove up to Stevens Pass on US2 this weekend for skiing (not in the Supra!) and I definitely wouldn't take the Supra up there unless you have some kind of winter traction tire. Even if the roads are clear when you set out, the weather can change very quickly and if it starts heavily...
Toyota of Tri-Cities in Kennewick, WA is an MSRP dealer with no mandatory dealer add-ons either. Although they don't do waitlists (you can put a deposit down on a vehicle they have an allocation for), and they've only gotten a few Supras this year.
EDIT: Should probably mention they only sell...