LOL @ stock suspension takes it no problems with the wheels you stated... I have an MY11 wrx with 18x9.5+30 and prior to that had 18x9.5+48 (stock being 17x8+53) each with 265/35/18 tyres respectively. Which, with all calculations gives an almost perfect overall diameter to stock. I can tell you, there is absolutely no way that stock suspension "takes it no problems" the amount of issues with it is ridiculous, heaps of suspension work was needed to give it a proper fit and without any rubbing. This is talking about the widebody wrx too, which you can fit much larger wheels in than an 07 sti... Just some information for you to think about.