I currently have a a CMD 121p which I stack on top of a NY 12 extension cabinet which is the same size, the 121p is insanely small and lightweight for what it can do, and is probably my preferred combo given weight power size. You can tell quite a difference when the cab is added in the bottom end, and of course you then get the full 500 watts!
I've also had the CMD 102p which is also great, loud, still pretty light, and an uncomfortable one handed lift. I have had a walkabout 12 before I which I really loved, I keep thinking of swapping to a walkabout again, but never quite take the plunge. To my ears the walkabout sounds better, but not much better, and the Mark bass stuff is just so usable, light and small......
I've never used the 121h before, but do sometimes consider swapping my extension cab for a 121h?...