I am in the same boat as you. This year I will be buying something else and for me it has come down to the Cayenne or the X6. I have test drove the Cayenne turbo S and it's amazing. But the feel of the road is different. Which is understandable. But every time I see a X6 I fall in love with the look. I have not test driven one but I will soon. If you get the 35i there are all kinds of performance softwares available to boost the HP. But if you get the 50i it all ready comes with 400hp and with a chip you''ll be around 460-480. I really like the look of the X6 and I think you will want adaptive drive. I could live with out the heated steering wheel.

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2010 X5M /// R63 AMG...Wifey's 540HP Family Hualer

2001 X5 3.0i Sport 335,448 miles & counting...
SMG M3 Steering wheel
E46 Stainless Racing Headers
4.6is Exhaust
Turner Pulleys
Afe Intake
Brembo drilled rotors
PowerFlex Bushings
Hualingan
30mm H&R Spacers rear
20mm H&R Spacers front
Bavarian Autosport High-Performance Coils
Active Autowerke's Performance Software