I am shopping for tires now, too, and have yet to find a better deal than Tire Rack (as long as you have a decent priced installer). You might check Discount Tire. They were only $10-15 over Tire Rack on some tires and they also install so might be a better deal in the long run.
'08 E92 M3 :: AW/FR
:: HRE P40s :: Remus Race Exhaust :: RD Sport Rear Bumper