Tarmac there's certainly some strange suggestions coming across now but I think the two you were originally considering, the X5 or the Cayenne are the best in this bracket combining 4 x 4 capability, prestige, luxury and comfort.
My personal favourite with my short and limited driving of the two is the Cayenne is best if you're looking for prestige and the way it makes you grin whilst driving it..........on the other hand the X5 is superior in regards to the actual appearance. The Cayenne seems to sit just too high and miles above the road and rims (unless you put some 26" chrome spinners on ) whilst the X5 with it's front bumper and step plates seems to sit less like a 'boat on wheels'! The handling on both is very similar but I feel the X5 has slightly less roll.
Good luck with the search