I had an Interlagos Blue M3 with Competition package a few years back, and I went to an X5 3.0si. I felt lost. But with my 4.8i and 35d E70...I do not miss (usually) the M3.

With the Porsche and and E70..you'll be great. 2010 and 2011 models have better iDrive, and with a pre-owned 2011 you'll get the great new tailllamps and bumpers.