I'm considering doing the CIC upgrade as well and I think if you're spending money it would be insane NOT to go to CIC or even NBT.
If you don't care about HD Radio then you can go with a unit from outside the US. If you do then I'd recommend looking at salvage yards and NOT on eBay.
NBT Retrofit:
>>> Bimmer Retrofit: NBT Retrofit in E70/E71 <<<
CIC Retrofit:
BMW E70 X5 CIC Navigation Retrofit - Done !
Part of me thinks the NBT makes more sense since the combox is built in and it has more features for about the same $$.