Not a huge powder ski know-it-all, but there's a fair amount of talk on these boards about Elan. I just bought Elan 666's (76mm at the waist, so a mid-fat by today's standards) and they are fantastic. Elan likes to put vertical sidewalls on their all-mountain skis and while these certainly do not carve like my old Atomic's, they do a damn good job considering their size. They rip, chop through crud, and float well in smaller amounts of powder.
Elan also makes 777's, 999's, and now a wopping 1111's. The 999's have gotten good reviews (99mm at the waist). People might suggest Rossi B3's or even B4's if you're looking for a dedicated powder ski, but you said you didn't want it to suck on groomer's, so the B3'd be a better choice.
Older Volant Chubbs can be found amazingly cheap still sitting around and seem to have somewhat of a cult following. I run into younger guys on them at Mammoth fairly frequently and people seem to love them.
Now for someone with some actual knowledge to contribute!