call the dealership for wheel offsets. but you can also just call different tire/ wheel shops for detailed info on it. places like tirerack and discount tire should know the common offset for each vehicle type.
since your car is a awd, i'd go w/ same size tires, so you can rotate them. (but that also means you can't get high perf directional tires..) not sure if you are going for a/s or high perf tires. but try to keep the sizes the same if possible; it should save you money and headache in the long run.