Being the op, I appreciate the comments, very helpful. I actually have had to 'man up' lately, as my playing schedule has ramped up. But my back does pay the price sometimes.
The plan now is to have Mather's Cabs make me a head cabinet, and pair that with a single 12 cab. You hit the nail on the head when you talked about tone. I've heard that the tone improves with a separate speaker cab, but my guess is that it has to be the right one. There are lots of them on EBay; some are slanted, extra large, compact, etc. I'm thinking that a speaker needs a little room to breathe, as well as being open back.
Anyway, Mather gave me a quote, and it's not too bad, if you mount it up yourself. I know that the two will weigh more together than the combo, but I'll be lifting less weight each time. But I'm sure I'll be adding an extra trip to the car.
Like I said, these are all good problems to have. I'm not complaining.
Best to you.
pusher