i've been going to the same place for years for all of my tire needs. i chose them for their best-in-town prices, service, and tire recommendations.
i called them up the other day about winter tires/wheels. basically i'm looking at $800 for either 16" steelies+Dunlop Winter Sport 3D's or 18" of the same tires (no wheels). so it's a wash to go either way, with the exception of $25 per winter/summer swap on the 18" wheels.
the guy also mentioned that i should retain much more of the handling performance with 18's than 16's, and the 18's were his recommendation.
so the 18's is what i'm going to go with, seeing as there is no price difference. i could possibly save a few bucks by going with Tire Rack, but they won't give me the service that my local place does. if the winter months chew up the stock wheels (which i doubt..?), then it's just an excuse to upgrade to a nice summer wheel.