Well getting new wheels is going to be tough for the X5 since I don't want to go down to 18" for my 4.6is (I don't have the original 20" for this one)

However, I did play around with the numbers and if I go UP a tire size front and back, there are many more options.

For instance, if I increase the overall sidewall by ~ 3.5%, there are a lot more choices.

That means I would be running a 255/55r19 in front, and a 275/50r19 in rear. There is a less than 1% difference in size between the two tires so should be fine for AWD (there is a 0.3% diff between the factory ones, these tires have a 0.7% difference)

That's probably what I'm going to do. I don't think a little more sidewall will look bad on the SUV and at least I can get some affordable all-seasons.