Okay, I read through the thread and re-read the OP. Here are my thoughts:
Your wife is pretty cool. Let her know that this fact isn't lost on you.
Spend some time playing as much as you can of the gear you're interested in. It doesn't sound like there's an urgent need to get it done now, so take your time and make a few trips, spread apart, if necessary. Bring along your current rig so you can play them side by side (your 121H combo atop a 12" extension cab next to one of the Ampeg heads atop a 410/212/610/810 should make for some interesting comparisons). Play at different volume levels (soft, loud, pushing it).
If your wife would be into it, take her along and make a day of it -- get a nice dinner some place, see some sights. She might enjoy being part of the process. (If not, spare her.)
Make sure that you can fit the rig in your car (you mention a small wagon) and get it into your home (if that's where you'll be keeping it).
If you've never played a tube amp or a rig much bigger than your current combo, it's worth taking some time to get to know what's out there. Even if you end up getting the same rig you'd planned on at the outset, you'll make that decision more confidently and feel better about it.
Good luck. Have fun!