Thanks brained,
I was raised on Atari 2600 :)
To answer your question about the damage on your cab...
I could'nt really tell from the pic exactly what is wrong, however bondo is king for speaker cabs, arcade cabs and rusty cars.
On my cars I leave the rusty hole as is, I don't punch out the rust and damage as it helps to hold the bondo while it cures, perhapse you'd have good luck just applying bondo to the damaged part of your cab then sanding it down with 60 grit on an electric/pnumatic sander.
Drilling 1/8" holes where the bondo will go will help to secure it (like tree roots)
If you want to fill in some of the button holes or holes in general you could tape off the back of the hole with duct tape, then apply bondo to the front, tip/turn the cab so gravity pushes downward on the bondo as it has a gravy like consistancy for 3 minuites and will run.
Bondo rocks!
Here in Maine (USA) we get a ton of snow in the winter, and the city trucks spray salt on the streets to melt the ice, as a result the cars rust and need the bondo treatment eventually (especially in the wheel wells)
Dig it?
Craig