Joe, this thought is worth exactly what you paid for it...i ordered a 'frontman' a couple years ago. at low volume, it sounded like a fender amp. anything above 2 (and it had no volume at 1), and it did something to the sound coming out the speaker that sounded harsh to my ears.
i have liked the sound from a couple digitals that are not way up in price...the electro harmonix 22 Caliber and the Roland cube (i did respeaker the cube i have with an Eminence 10"). the electro harmonix is about $100, but you have access to a pretty good speaker already...if you can get a few scrap pieces of 1/2" or 3/4" ply, you would be in business with the little amp (it's the size of a boss pedal, and is 'amp only', but sounds pretty dang good to my ears).
if you took the 10" Celestion out of the Marshall, and stuck the stock one back in, a cabinet is not hard to build. (i doubt anyone would give you $5 more with the Celestion in it-anytime i sell anything nowadays, i take any 'extras' out if i can use them elsewhere). i got to emailing with the Eminence people, and they turned me onto using truck bed liner for the cab covering. it actually looks pretty cool. the speaker hole is the most difficult thing to get exactly right...at the price of plywood nowadays, i 'measured' about 5 times and cut once. if you think you want to do this, i'll tell you what i know about it...not an expert, but built a half dozen serviceable speaker cabs last year.
