Its been a while, but there's been plenty of slow, steady progress in that time...
Got some sideart , with massive thanks to JDfan.

Had some router problems, well documented here:
http://forum.arcadecontrols.com/index.php/topic,132630.0.html
Part of the problem was a cheap, badly suited router. Part of the problem was that i assembled the cab BEFORE routing (bad idea). Part of the problem was that I am evidently not very good with a router !
Apart from the slot cutting, the other most difficult part was the paint. I found it really difficult to get a perfect matt finish with spray paint. In the end, I just kept spraying, fine sanding, spraying and sanding, until I settled on a reasonably good finish after about eight coats.
The T-molding needed some hot glue to help hold it in place. This was actually my first experience with a hot glue gun - loved it. Now everything in our house has been hot glued. I will remove the cat from the ceiling as soon as I can (just kidding).
I used one of these for sound:

Okay so its its not the most powerful set of speakers in the world, but I am mainly interested in pre-1985 games anyway, most of which used fairly insubstantial mono speakers, from what I recall. As USB speakers go, these don't sound too bad at all, plus I found that the cab itself helps as a sounding-board for a bit of extra bass.
The cab is more or less finished now. I am having some i-pac issues (a separate thread), and I am not yet sure of the best way to hide the edges of the plexi. But the kids have been enjoying playing it.
We discovered the delights of 'Juno First' the other day, and have been having a Juno-fest hi-score battle in our house since.
I will post some pics of the finished cab here soon.