I personally think a spare car is needed if you want to own an off warranty, higher mileage X5. V8's especially. Then if a the X give you trouble, you park it while shopping for the best price on paying someone to fix it or to find the time to shop for the best prices on parts and the DIY that follows.

OP, sorry to hear about your troubles. A second on driving the Mazda 6 as well. Car and Driver has a nice review on both of those cars.

__________________
2004 E60 545i Sport 6MT. Black/Black Build Date 6-2004 102k miles