With your factory GTS style 14" wheel and tyre combo you are looking between 25 and 26" diameter.
So if you go up to 17" rims you will require a 45 series sidewall profile tyre to sit into the same 25 to 26" diameter.
You probably could go up to a 27" diameter if you wanted, but you would just have to watch turning on your front guards.

Staying in the 25 to 26" range something like 245/45R17 on the rear and 225/45R17 on the front would work fine.