Just to add to Dan's post ... another option is the Mach V Awesome wheels 17x9 at +42mm offset. The 255/40-17 tires will be almost the same diameter as the 255/35-18 tires. The 17" tires will have a slightly taller sidewall than the 18" tire but it will be a shorter sidewall than the stock WRX tire. The 17" tire will usually be cheaper than the 18" size and have a slightly cushier ride due to a higher sidewall (assuming same tire models). But the downside is that the 17" tire will usually be heavier than the 18" tire (same brand/model) - and the extra weight is on the outside diameter of the wheel/tire combination - which is the worst place for acceleration. Most people don't care nor will they notifce the difference but it may be something to consider.