Welcome aboard! I'm a noob as well (2 months with the x5d)...all i can say is it's a great vehicle and we're very happy with it. It's a diesel so getting extra power is easy, but as for any car now days, the price of getting caught is high. Havent seen anything on a x6d for the US....nor any news of the x40d being US bound either.

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2011 X35d - Platinum Grey/Black/Bamboo
Premium, Convenience, Technology, Rear Climate, ipod/sat - 1st Time BMW Owner

2006 Dodge 2500 Diesel (7500lbs and 13.4 Sec Qtr Mile)
2010 KTM 530 & 300