The KDWS's are on special from discounttiredirect.com and tirerack.com for under 100 bucks. Get them while they're still available! They are replacing them with the Super Sport All Seasons, and they do not come in the 235/50/18s.
I checked mine on the car and thats the size. I can get them for $75 from another site, tires-easy.com. That's my only concern... if I screwed up and bought the wrong size.... plus getting tires makes me want rims... and I like the Razors.... a lot. Not a good thing.
I have Pirelli P-Zero Rossos and I love them. They stick good rain or shine. They cost like a million dollars though. Seems to be the trend with any 19" x 10" rim though.
Those were on my stock 17's which I sold for $500 early last year. My dad had Pzeros on his 911 when I was growing up... so naturally I trust the Pirellis.
I just replaced the 18" KDWSs that came on my '06 GT with Michelin Pilot Sport A/Ss. Absolutely the best tire I ever drove on. Fantastic on dry roads, in the rain and even in snow. Pricey, yes - but worth every dollar.