If you can swing $550 + shipping, the 
MAMERoom Designs kits are supposed to be excellent and snap together like most assembly-required furniture.  It's probably the cheapest and easiest tool-less way to go.
Wow.  Snap together.  That's awesome.  I may end up getting one of those - lazy-ass that I am.  Probably end up using an X-Arcade controller, too.  (much cheaper than the controllers on that site - you can get a two-player model for under $200.)  BTW - the X-Arcade site *sucks*  None of the links work for me unless I turn off Javascript.  That's garbage.
Anyway, it's great to know that such an option exists.  I would still like to design my own, (and I'm sure I'd save money that way.)  But we'll see what happens.  Thanks for the link!