I would suggest a p245/40zr18 michelin pilot sport ps2. pretty much the best tire out there. yokohama is low-budget.
you say that, but have you run a pair? They are cheaper without a doubt, but I have to say they are one of the best running tires I have used yet.
I have a pair of Yokohama Avid V4s tires on a Grand Prix with Koni's and a rear sway bar and I can push the GTO (that has Koni's and Hotchkis) through turns in the Grand Prix without the tires making a chirp, squeak, or sliding.
To top that off, they are only $78 each in the Grand Prix size. Now while that particular tire isn't made for the GTO, if it was I would run them in a heart beat seeing as that I don't get more than about 10,000 miles for a set of rears in the GTO.
Yes, the Michelins may grip well, but if you are driving them hard and wearing them off just having fun, you cannot beat something like a pair of Yokos for the money and traction that they do offer. Besides, who wants to pay $230 for a tire that you will just be beating on all of the time.