The 18s will fit but you need to be careful with the offset and backspacing. OEM 18 inch wheels usually run different specs than the 20s so measure before you buy. As far as the brakes go the A Spec has the same rotor and caliper setup as the base model so that's not a concern for you. The tire selection thing is real though. Winter rubber in that 245/60 size is night and day compared to what's available in 265/45. You'll have better prices too. Just make sure whatever 18 inch wheel you pick has the right bolt pattern and offset or you could end up with rubbing or clearance issues. Got photos of what you're looking at.
