We're about to start on the LAN robot using the VIA board and your controller. Any reason we can't use the AX3500 rather than the AX2550 and so save a few bucks?
As long as the current on each motor doesn't exceed 40A continuous per channel, the AX3500 will work just as well. Beware that the AX3500 is sold as a board and that you will need to carefully protect its electronics from loose wires and metal debris.