if you want to keep your stock wheels for winter and get something bigger for summer like me; i have General Altimax Arctic and i love, love, love them! low road noise and excellent grip! i've gone though a foot of snow with no problem and my stopping distance dramatically decreased!
at only $292 for the set of 185/65/15 on tirerack, which will fit on the 2's wheels it's a really good deal!
"Narrower winter tires are better for cutting through plus tires are cheaper in that size." <<< this is definitely true!
also remember that the second number such as '65' is just the sidewall height, so you can change that without changing the wheel size.