I'd suggest something like the Head iM88 - it's great when you get powder, but it rocks even on the hardpack (it basically skis like a GS ski, just a little slower edge to edge). It's really good fit for what you're looking for I think. It's one weakness is bumps (doable, but gotta work for it). The iM82 (same construction, different dimensions) skis similarly, but is better in the bumps.
You may also want to check out the AC4, which I dont' know much about, but I hear it's similar to the 88 - good for goin fast on hardpack and great in powder, but I'm not sure if it's as versatile for stuff like trees etc.