small update: still have yet to start the build, but it's probably better that I've been delayed given the updated layout!
Yesterday, however, I managed to score a good deal on an unfinished 12" speaker cabinet on ebay that should be just right for housing the new amp! I don't mind a little woodworking, like doing the cutouts, but I'm really not prepared to build the box from scratch. I looked at some pre-fab options, but didn't find anything exactly right so I've been keeping my eyes out for a deal.
Saw this yesterday - slightly larger than the Trinity cab, so I know it will fit; might have to re-do the baffle, definitely the rear panel (I might be able to use the back panel to cut a new baffle & only have to fabricate a rear panel
).
Came across the auction with 5 minutes to go...$50 + $35 shipping, $85 cabinet.
w00t!