My previous vehicle was a 2009 Mercedes ML320 diesel, and while the X5 is better in almost every way, it's WAY noisier than my ML320 was.

Part of it may be the run-flats, and I plan to replace them with a set of Kumho SOLUS 4S HA32 SUV tires (same ones I had on the ML when it was written off... quiet, smooth, and functional in snow), so that should help.

I never needed to close the (smaller) moonroof in the ML, but the beautiful panoramic one in the X5 is a huge part of the noise factor, especially at highway speeds, so I've grudgingly learned to close it up accordingly.

Any other suggestions?