I would steer toward the Cobra over the SL, or Heritage as a second deck. I would go with the Heritage over the SL as well.
Reviews say the Cobra has similar characteristics to the SL, but with a shape suited for powder. You'll be able to take the Cobra all around the mountain and would love it on powder days. Which you say you see (bastard).
Also as a second quiver board for mountain use only I would go with the heritage over the SL. The SL is playful and can be used for park. With only 1 board I would get the SL. The heritage is more of a free-ride deck and less of a park deck. Neither the SL or Heritage will be as easy to ride in the powder.
Cruising the mountain and enjoying powder, I'd go with the Cobra. On bad weather days hit the park with your Evo. What's the point of a quiver if you get a board that tries to do everything OK like the SL?
I was in a similar position to you last year. I had a cheap park board to learn on and upgraded at the end of last year. I demoed the SL and Raptor among other boards. I bought the SL, because I typically ride small hills with around 700ft of vertical. The SL is playful. The Heritage would be a little stiff for what I typically want to do on the mountain.
The Raptor was my favorite board I demoed in Killington, Vt. The Raptor was amazing for hard charging and carving. A pure dream to ride. I've been thinking of what my last day of snowboarding was like all fall. Too bad the board is useless for 95% of the riding I do. I wanted a one board deck. The Raptor isn't it.