Sorry, thought I remembered more detail in their iso-box links - this is the only one with much of anything, and it's not much unless you're already experienced in this sort of thing -
http://www.amptone.com/g078.htm
If you can get hold of someone's old burned out dorm refrigerator that still seals, you'd be surprised at how much attenuation you can get from a frig - I stuck a boombox in one a few years ago and shut the door while pointing a sound level meter at it - level dropped by over 30 dB when the door was closed.
If you can find one that doesn't work anymore, you could build a speaker baffle and mic holder (or place the amp inside, although it could overheat in some cases) - probably the best way would be to drill two holes through the walls (the bottom probably wouldn't have any cooling coils if you can miss the compressor itself) - drill these holes just large enough for a speaker wire and a mic wire, then install an extra speaker and baffle (piece of plywood with a hole in it for the speaker) - get one of those little mic mounts that Rat Shack sells
http://www.radioshack.com/product.a...y_name=CTLG_007_008_002_000&product_id=33-332
and a short gooseneck, mount it all up (look at the Demeter box for ideas on this)
http://www.demeteramps.com/proaudio/ssc1.html
Then, just plug a speaker cord into your amp (hopefully it has a jack for external speaker, watch the impedance carefully if it's a tube amp) and run it into one of the holes in the frig, ditto the mic cable (you'll need to be able to solder in order to keep these holes as small as possible, and you'll need to get some silicone caulk to seal the holes afterward)
Gotta hit the sack, hopefully this gives you some ideas - or, you could just go buy the Demeter box for around $600 - I haven't heard it, but it's gotten some pretty good reports... Steve