to add the controllers, all you would really need are open USB ports. i had my 2 player cab set up like that for a while. not so much for playing other emulators, but i set it up so i could use the xbox gamepads for players 3 and 4 for a few good games of TMNT. are you planning on leaving them connected all the time? if not, you would have to make sure you plug them back into the same USB ports, and in the proper order to make sure they work as you want them to all the time.