18x9.5 +38 would be flush rear and fit fine front, guards can fit alot in when you give it a go, and the outcome is worth the effort. Wider wheels in the same diameter from rota are the same price. Depends what you are going for with tyres, if you're going for all out form > function with these set of wheels and tyre combo (which i presume you are). I wouldn't go any bigger than a 225/40 on either a 9 or 9.5, good stretch and looks good, once again if going for form>function.

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MY 04 WRX