Here's my opinion or suggestion.
For winter driving, buy a set of Bridgestone Blizzaks for your stock rims 205/60/15. Then you won't have to be concerned about winter damage to those 18 rims your wanting. The Blizzaks are fantastic on ice and great tractions in the snow. You will have confidence for whatever winter has in store.
Save the 18" rims for summer driving or whenever winter conditions are over. You will also have a better choice of performance tires to select from.
This of course will be the most expensive solution but it's the best for confidence and safety.
Buying an all seasons tire for an 18" rim may sound good to you but.... I am a professional driver and every winter I see those dudes with the wide tires never doing so well on the hills in the winter. Duh.... I wonder why?
