when I called the tyre shop they said that the 205/40/R17 are a rare tyre as this is what I have on my CG8 atm but the 215/40/R17 are cheaper I told him what car I was going to be putting them on and he said that they will be fine he I was looking for another set of kumho tyres and he said that they fit these ryres to alot of skylines so they will be fine for wrx.
I will look into it a bit more before I get them to make sure im not going to die.