UCCNC will only work with one of the CNC Drive motion controllers. They basically supply 4 controllers, UC100 which is a USB dongle type unit that then plugs into any standard break-out board. This I believe works at 100Khz, which is still more than enough for most stepper systems.

The next is AXBB-E which is a Combined Motion controller and breakout board in one nice neat little package. This uses Ethernet and runs up to 400khz.

The third is UC300ETH which is just a motion controller but provides the equivalent of 5 parallel ports worth of I/O. This again can plug into 5 x standard Bob's or can be matched with dedicated boards like the UB1 or CncDrives UCBB which is a dual-port board. This board is the most expandable of the boards in terms of I/O.
They also do a USB version of this board but you'd be mad to buy one as USB is a pain in the arse for CNC.

Last is the UC400ETH which is basically the same as UC300 but with only 2 ports and without the Analog I/O.

In your shoes, I would without a doubt go with the AXBB-E as it's neat and simple, provides connections for 4-axis, and allows expansion using a separate BOB to increase to 6-axis if required. Does everything the UC300 does because basically, it is the same as UC300, just with less I/O capabilities.