I very much disagree w/ tromano on this. Getting on gear appropriate to snow conditions and your weight will make learning a ton easier.
I agree with doing some renting if convenient. My .02 of a few things to consider given the "mission":
Ideally, I'd look for "fat" and tip + tail rocker with either reverse or zero or very minimal camber. Probably early taper (which may not be "obvious" in some designs). A pintail makes powder easier. Hence I'd be careful about jumping into something like a Hellbent (esp given its softness) as the wide tail - whose mission does nothing for you at the moment anyway - can actually catch under some conditions if you are not moving right along. Even though it is much stiffer, I'd think about the Caylor in a similar way.
-189 K2 Pontoon (blue& white or Tribute as they are a shade stiffer than the original)
-195 Volkl Kuro
-202 Praxis Powder Board (maybe even the 195)
-192 Praxis H20 Heli (this could actually be a huge win, all things considered)
-contact ON3P and ask when that new thing (search for thematic not-quite-NSFW pictures) will be available
Relatively speaking, these will all make powder a dream. The longer Pontoon and Kuro are not as nimble as their slightly shorter siblings - but at your weight & experience level I think you will want the length. They are still vastly more nimble than any "conventional" ski. While not quite as progressive in some ways, the H2O has a ton of surface area with tip rocker and some tail kick - and based on discussions with the H20 guys I believe the flex is well thought out. None of these will be a ton of fun on groomers. But all can be managed decently back to the lifts on anything short of ice.
If you want something more groomer friendly for those in-between times, think about...
-195 Rossi Super 7
-192 Atomic Bent Chetler
-190 DPS 112RP
-187 Praxis Concept (maybe just a bit too short...)
-just based on looking at them, Movement Super Turbo (either size)
None of these will be quite as easy as the first set in powder (which is why I'd focus on the first list). Especially if you are dealing with breakable crust or deeply layered snow. However, all will be easier in powder than a narrower ski or a more conventional fatter ski.
Search will likely reveal other threads here & at TGR covering similar discussions. There are probably candidates I have overlooked, but the theme should be pretty clear...
Edited by spindrift - 3/7/11 at 8:27pm