I've just remembered about this thread!
Well, I did finally get around to building a retrobox and it literally is a box, or a cube as it's marketing name implies.
I have to say, I'm really getting back into emulation since buying a dedicated machine to become a substitute for my lost youth. Shown below is an Aopen X-Cube - an inexpensive SFF PC that does nothing but run emulators!
Inside is my old Athlon XP overclocked and running at 1500Mhz; along with it came my 2 sticks of 256MB PC2100 DDR, but now running at 150Mhz (300Mhz DDR); the chipset is nforce2 using the built in integrated graphics in dual channel mode with TV-out.
Also intend to buy some arcade sticks next. Considering the Logic 3 ones shown below as they're cheap and have USB, playstation and X-Box connections as standard! The other option is the mighty (and expensive) X-Arcade 2-player station, but they have a serial connector and you have to buy adaptors separately.