For a 2-player panel like Floriske.nl's you'll need:
* 2 KADE miniArcade boards from
here (or 2 Minimus AVRs if you want to save a few bucks and don't mind soldering)
* 2 USB to X-box adapter cables like
this* Wires and quick disconnects.
Paradise Arcade Shop has prefab 16 wire rainbow packs and daisy-chain grounds that make wiring a panel
much easier.

Check out the
Quick Start guide for links to the KADE Loader software and directions. (works with the Minimus AVRs)
Scott