Quite a nice image. I like the rocky ring in the background and the foreground texturing especially.
Congrats on the new system, however I think you are perhaps making the error of turning up settings on new hardware unnecessarily. For this scene, detail 0.8 may be ok, but 0.75 or even 0.7 would probably be fine. More importantly, AA8 is almost certainly unnecessary as AA is much more important for objects (especially vegetation) and not so much for terrain. AA 4 or at most 6 should be fine for this scene, especially since you appear to be adding sharpening in post processing. GI 4/4 is really quite high as well, especially with the higher detail setting. Your shadows are not terribly complicated here. I would say GI 2/4 should be good. That should cut your render time perhaps in half if you lower settings as I suggest, and quality should be similar.
Again, nice work.
- Oshyan