well, I always get winter rims. Saves my summers. Winters here would kill my summers if I didn't.
Second, I always drop usually 2"'s in diameter, and I do this because a 16" tire is a lot cheaper then a 18". You just need to make sure you get the right sidewall height to keep the overall diameter the same. I haven't checked yet, but I'm guessing 55 series if I go 16.
Also, it's better to have a taller tire for deep snow, not to mention better ride on winter roads which can be bumpy due to frost causing heaving which happens here a lot, ice built up on roads etc. Thinner tire is great to cut throw the snow of course, but you guys have an entirely different winter them we do up here so half of this doesn't matter.
17's will be my last resort. i am grabbing a 16 from the dealer to see if it clears the caliper. front brakes are bigger right? Haven't had time to check all these little details yet.