I went on a similar quest a couple of years ago, when I decided I needed something lighter.
I was happy with the sound of my Trace gear, but my back had had enough!
I have bought, and sold lots (too many!) amps and cabs before settling with my current rig.
As has already been mentioned "The world is your oyster"... it is also a potential minefield.
On reflection, it might have been easier to change cabs first, then replace the amp?
There are quite a few lighweight 15's out there, but don't dismiss the possibility of a good pair of 12's.
Good luck.