Good evening,
The SH6868EP is simply an extended performance 6868 cable. The main difference is that the analog pairs are twisted to get the maximum noise cancelation out of differential measurements at higher speeds. The SH6868EP is better at rejecting noise. The pins through are the same though, so you could use your SH6868 with the PCI 6052E series. I would recommend looking at the M series boards as they are the same price and have more functionality, with the ability to do correlated DIO, as well as better speeds for the same price. Please let me know if you have any further questions about this issue.
Have a great day,
Michael D
Applications Engineering
National Instruments