I just ordered a set of Invo's for my GTP today. Pretty excited!
I decided to go with 255/50-17. They're a tad taller than stock, and quite a bit more so than the 245/45's I was running on. I got a pretty good deal on them, too - less than $500 shipped to my door.
I'll get some pics when they get here and some more after they're put on the car.