I think L series low or even forester low with the diffs you have now would be adequate. Also L series low wont fit with 4.44's without serious shaving down result in weakening.
IMO people downplay the affect of power (more so torque). We went on an offroad trip with me driving a borrowed GT Foz with HTs, there were two lifted SGs with ATs and Tazas foz. This was in beach/dunes.
The GT had by far the easiest time of it.
For rock crawling IMO the 2.5 with 1.19 is just better than a 2.0 with SF low range. Its all about balance otherwise as Rally said one big upgrade will just highlight the weakness of other aspects of the car.
2.5 with 4.44 and SF low, or 2.5 with stock diff and L series low seem the perfect combination. Supercharge the 2.5 and you have a very hard to beat subi offroader that will be better than most stock- lightly modded 4x4s on sand and better than pretty much any 4x4 on the rocks.
EDIT: Thinking about it, all this talk of what beats what is losing what offroading subis is all about. Its about fun!