I'm in the same position as you are. I chose to go with a wheel/tire package from Discount Tires Direct. I'm getting the Konig Reign wheels (16x7) and Michelin Pilot Alpin tires (205/55-16).
Here's the wheel:
I picked this because it looks pretty close to the factory wheel design (17"). I would never be able to choose a wheel with another design over the Internet. I'd need to see it in person. That wasn't working because no tire shops in my area had any clue as to what wheels would fit the IS (when I was looking a few weeks back, even TireRack only had 2 16" wheels to choose from). I was very happy that I found Discount Tire Direct with such a large selection and that Konig makes a wheel close to what I wanted.
At about $100 per wheel and tire, the whole package comes to about $920 with shipping and lugs, etc. Not too bad, since buying good winter tires in 17" would be at least 2/3 of that. I don't have them yet because the tires are on order.
Good luck,
Rob
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2001 IS300
Spectra Blue Mica/Ivory
LS, LD, HH, SR, 17" wheels
2000 Jeep Grand Cherokee Limited
4.7L, QuadraDrive, UpCountry
Patriot Blue, Fully loaded