What is Cat 6e or Cat 7?
As far as TIA (Telecommunications Industry Association) standards go, Cat 6e and Cat 7 do not exist. Standards for Cat 6e or Cat 7 have not been approved by TIA; therefore, Cat 6 is currently the highest TIA standard for twisted-pair communications cable (As of 3/02/2008).
If you see cable called "Cat 7 or Cat 6e" (or some other higher number), that is just a name that a company made up to put on their cable. One manufacturer's Cat 6e or Cat 7 could be built by totally different standards and specifications than another manufacturer's cable.
So, if you still want to pay the extra bucks to get Cat 6e or Cat 7, just know that you will be getting cable that could be made anyway the manufacturer feels like it. To me, your best bet is to go with Cat 6 cable, this way you can rest easy knowing that your cable is up to standards.