I don't know exact specs on the difference between the 4.4 non sport and the 4.4 sport package, but I have the 4.4 sport package and it handles amazing for an SUV. The suspension feels a little firmer than the non-sport, the wheels are bigger/look better and you get the clear corner turn signals.

I agree that I would get the newest model that I could afford and be sure to get it with a warranty.

I would look out for oil leaks, coolant system leaks, torn CV boots and be sure to check all windows and electrical gizmos. If you do a search there are many threads on what to look for when purchasing an X5.

The SRT is balzing fast, but will not give you the overall driving experiance that a 4.4i sport package will. Besides acceleration, there is no comparison between the two, IMO. Everything else is better about the Bimmer.

Good luck.