How much do you weigh? It makes a pretty big difference in the width of ski you may want to choose.
I know it is tough due to wide skis, but try and demo if you can. I have found that wide skis diverge pretty quickly in terms of performance, even those that are somewhat similar in dimensions, camber, sidecut et cetera. Some that "should" be great at speed in crud aren't, and some that look like deep-snow only skis tend to be surprisingly versatile. Hard to say for sure without demoing.
From your description (new snow for a couple of runs, cut-up the rest of the day), those conditions seem to shout for a really wide, all-mountain ski over something powder-only; something like the HT. Much of Tahoe is so steep, that it is so easy to release at the end of the turn, as it is a matter of just relaxing, letting your body float, and allowing the skis to release and float up, that you probably can get away with something different than if you were skiing deep snow on low-angle snow, where a really wide reverse sidecut ski would be more useful, due to lack of momentum/gravity. Around here, something like a Pontoon or Praxis Powder can allow a skier to ski our low-angle 20-degree slopes that aren't access-able on normal skis. Then again, you do get a lot of heavy snow, which could cancel that advantage out.
You have probably read my review, but I had a blast on my Elan 1010's last year at Squaw. I couldn't imagine a better all-day wide ski for that resort. But, it sounds like you don't want an everyday, 6-18" new snow ski: you are looking for that really big ski that floats on anything. If that is the case, then you might want to go bigger, with a tip designed first and foremost to release in lousy snow. You can always go back to the car and get the wider all-mountain ski when the terrain gets cut-up.