Don't worry about the engine although I did the whole time once mine was ordered too. Once I got it, I've had no regrets. It's quite powerful, especially in sports mode.
2015 X5 Sdrive 3.5, Black Sapphire, Black
2014 328i Gran Turismo, Jet Black, Beige
2013 X3 28i, Alpine White, Mojave Brown
2010 335i Sedan, Space Gray, Sport, Premium, CA, (retired)
2008 X3, Alpine White Sport Package - (retired)
2008 X3, Crimson Red, SA Package - (forcibly retired)