I am on the fence for long term as to continue running GS which I am now greatly out matched by the celica GT-S, Cooper S, and RSX Type S or moving into STS.
I love running on R-compound tires. There is no feeling like it. But I know I will like the daily driving of my car set up in STS better. So until I get the money and make up my mind I will run in GS and continue to have fun. I don't plan on winning nationals in my lifetime. This is a hobby for me and if I can do it, enjoy it, and not spend my life's money in it and still be occasionally close to the guys winnings national and regional events, then I am a happy man.
If you feel that your driving is not the problem with your performance on the course than don't get bigger rims. There is a reason that really great drivers run in 14 or 13 x 9 rims. Besides the fact that they are lighter.
R compound should never be compared to any street tire. Thats like the difference between a set of Kmart special gulf clubs and a set of Calloways.
If you have already set the wheels of the deal in motion, I hope you are happy and continue to have fun.
Good luck and hope to see you out there on April 6th. I drive the 2003 Honda Civic Si with the goofy rims.
Rob