I am currently running 17's on my GT. 245/65R-17 Bridgestone Blizzak DM-V1 SL on 17x7.5 Sport Edition F11 Silver Rims. Basically the TireRack package. Speedometer is off about .5-1mph off but other than that, the ride is good. More quiet than other snowtires I have had before (Firestone Winterforce on a Toyota Sienna and Dunlop Graspics on a Protege5)
I've had 17" snow tires from tire rack for two winters now - they work well. I really appreciate the extra cushion for the potholes:
http://www.mazdas247.com/forum/showthread.php?123835669-Pics-of-new-17-quot-snow-tires