...a pic of the wheels I'm thinking of getting for the PA.
These are 16"* but I'm looking at a set of 18"*.

hrmmmm, i dunno. doesnt strike me as buick IMO

if you with 18"* you should go chrome man... 'go big or go home' you'll want smaller/lighter wheels for the track however

I disagree. Those look nice. No chrome, it cheapens the look of a PA

Definitely. There is very little chrome or shiny stuff on this car.
That, and I, personally, like the slightly subdued, old-school look on my cars, so no bling for me. When I get these I'll try to find some high-performance gold-line tires.
If I manage to get those Vette front brakes on the car, I won't be able to fit smaller tires/rims on it any more. And they'll look beastly sitting behind these rims.

so gxp rims?

Thought about GXP rims, but the look is slightly off. The spokes aren't really visually heavy enough for a car this BIG. The GXP'* would look better on a sportier car, but these speak a little better to the luxury-car side.