Alright, so I just posted an introduction, but I feel like this is an ideal time to ask this question.

I work on a Mac, which obviously brings with it the problem of not being able to use FractalTerrains. I've achieved decent results with running the "Lighting Effects" style of elevation (shadows and light, full mountainous, ect), but it really doesn't achieve the effect I'm looking for...which is something similar to what a2area did with his map.

To put it simply, I would like my maps to have the effect that real height maps and high-quality terrains have: a sloping effect...something I could put into Bryce and see a good-looking, natural-looking mountain instead of a couple smooth bumps and a wide span of flat ground.
I'm not expecting the same results as a dedicated program, but I was wondering if anyone had any ideas about how someone would achieve maximum realism with what I have? I've heard there are DEMs provided by the government that do something similar, but so far I have yet to find any.