Salomon Powder Snake, killer board - only $399. It's similar to the Sick Stick but without the bamboo.
Or if you want to get more spendy, try the ride slackcountry. It will plow through anything, and is unbelievable in powder.
Arbor Coda/ElementRX would be killer too. Tons of pop and great in powder.
Something a little more aggressive would be the ride highlife, you can take that board anywhere, it will destroy any terrain you can throw at it. It's super surfy in powder, but real stiff and damp so you can stomp over any mid-day chunder. A similar board would be Jakey B's Ride Berzerker, it's a little more playful, better all around board.
Now only the first two are powder specific boards, the others are great in pow, but will do better when you're not in fresh snow.