I used to want my own arcade system, but now I just want an enormous HDTV and a good surround sound system.
If nothing else, it does seem like it would be fun to put together though. Make your own plans for a cabinet if you have to.
A quick google search came up with this though
http://arcadecontrols.com/arcade_cabinet_plans.shtml . The first link had diagrams all drawn out.. fucking costs 2 grand.