What are your factory tire sizes?  You can plus size but if you do something out side that you run the chance of speedo error and or DSC errors.  A plus size for 205/55-16's, what I believe your factory size was is 205/30, 215/45, 215/50, 225/45, and 235/45 17's. Using these sizes keeps the tire diameter the same as the factory settings.  You can get this information at Discount Tire.com.