The 7I76E has all the features of the parallel port connected 7I76 plus more including two headers for connecting other Mesa daughtercards. Instead of the parallel port it has an Ethernet connection.
The price is the same as a kit with a 5I25 (PCI) or 5I26 (PCIe) "superport" card and a 7I76 board with connecting cable.
The downside? LinuxCNC currently doesn't support using Ethernet connections (or USB).
What CNC software does support Ethernet connected step/dir boards like the Mesa 7I76E?