AC3 or AC4
I am also a level 8-9 skier, 6', 225 lbs and purchased both 175cm Volkl Allstars and 177cm Volkl AC4's this season. I posted a review on the Gear Review Forum: http://forums.epicski.com/showthread.php?t=33760
Since that review I have an additional 7 days (Killington, Stowe, Jay Peak) in heavy/spring snow conditions, freshly groomed and hard pack/icy trails. The impressions in my review are still valid but I have a greater appreciation for the AC4's working well in almost everything. The Allstars excel in hard pack/icy conditions and also worked well in soft - medimum firm bumps. In heavy snow gun snow and wet (after rain) snow the AC4's were definately the ski to be on. If the bumps are soft, the AC4's also worked well, although not as quick as the Allstars.
For the AC4, the 177cm is a good choice. For the Allstars, while I like the quick turns I can make with a 175 length, I would probably prefer a 182 for more stability at speed. I also have a pair of Volkl 5 Stars (182cm) and find them to be a more forgiving, softer ski then the Allstars. But, having skied both, I prefer the Allstars.
If I had to recommend only one ski, it would be 177cm AC4's. If you can, demo, including some of the other skies recommended on this thread.
Good Luck - Charlie