Talked to the guys at Costco... they only sell Michelin, BFGoodRich and Bridgestone. Even withing these brands, they only sell a few models.

The guys there were telling me that one of the best tires for the X5 is the "Bridgestone Ecopia EP422". Reviews seemed OK on TireRack.com and I was willing to get them but they are on back-order and I cannot wait for 3 weeks.

They also said that the "Michelin MXV4 Plus" were discontinued (which is odd because their website shows that as an available option) and the direct replacement was another Michelin tire (I think it was the "Primacy" but I'm not 100% sure) which was $100 (per tire) cheaper. Didn't make sense.