I think the X5 3.0si will be adaquate. It's not going to be blisteringly fast or as fast as a lighter X3 3.0si, but keep in mind you are driving an SAV, not a 3-series. The engines have good low end torque and a 6-speed auto to keep it in the powerband. By the way if you don't know, the 2007 X3 and X5 3.0si use the same engine, a 3 liter inline-6 (not a V6).