WRX will have pretty expensive insurance. You will get a fairly decent break if it is a wagon though. I own a wagon in Canada. The base rate for my insurance in BC (21 when I first insured it) differed by around 700 per year - around 3600 for the sedan and 2900 for the wagon. Of course rates will differ province to province and state to state as well as by age and driving record, but those were the base quotes for me.
dont put one on unless your gonna mod your engine to similar as the sti, and ^^ mine is way cheaper cause mines a 97 i wanna get a 9-3 viggen they are the sickest saabs