I had a Logitech controller and got fed up with how crappy it was for playing fighting games, so I took it apart and did some piggyback soldering on the board and ran the wires to an old control panel that I had. I need to build a box for the panel, but it works pretty good. I wired the new buttons directly to the Logitech button board counterparts. Here is a video of what I am talking about. I might incorporate this method on my next project. All it will cost is about $20 for two logitech controllers. Lots cheaper than J-pacs or other interface units. And perhaps a knowledge of circuitry is helpfull.