You only have 2 choices, as far as I know: Bridgestone and Dunlop. The new C6 vette will wear identical size as our car in the front, and they're a new design made by Goodyear. I don't know if their weight rating will be enough for a 600+ lb heavier car though.
My '04 car thankfully came with Dunlops (Bridgestone tires are crap IMO), but I've only put 800 miles in 5 months, so I can't really comment objectively. They definitely feel very stiff; obvious when they have to support a 4K-lb car deflated. One thing I was disappointed at was the very shallow looking treads; they look as if they're half worn already, and the wear bars are right there. Hopefully they'll provide decent life, as they should being an all-season tire. We should learn about that in a few months, when '04 owners start piling up the miles. I'll also put run-flats again, even with their disadvantages, just for the piece of mind. Tire rack has them for $235 a piece, and mounting and balancing shouldn't be more than $200 I'd think, so $1,700 seems abusive. No dealer or Lexus warrant tires, so go for the cheapest place. My only concern would be wheel damage, so make sure you show your car to the manager before they touch it.
Please keep us posted about your experience.