Hi - Some of your question depends on your skill set and mission. A 4 hour walk to very steep downs suggests you're at least a high advanced skier, ideally an expert. But the 7 to 8, and the sense you've never done this before, suggests high intermediate to low advanced. Which is closer? Also, are you planning to mount AT on these? Tech? Or by "walk," do you mean hiking, carrying your skis on your pack? This makes a difference because if you plan to skin, then you want a lighter and shorter ski than if you can carry them. And along these lines, if you've never done this before, I hope you've taken backcountry training and are going out with experienced friends.
Second, how old are you? If you're still growing, it would make sense to get cheaper skis. If you're grown, obviously you could invest more if you want to, although I'd advise against sinking a bunch of money into your first powder boards.
Anyway, DPS's are nice skis, although $$ if you're just getting started, and they vary in their forgiveness. Some less expensive lighter skis that would work for hiking or skinning include Armada TST's (decently cheap right now but going fast), Elan 999's from this season (very cheap right now, great all around for on-piste and off-piste), Blizzard Bushwackers (which at your size would constitute a great backcountry all purpose ski that is, like the Elan, strong on groomers too), Praxis Yeti (very light in your length and on sale right now), and Prior Husume's (which are lighter than the DPS equivalent, but a bit wide for your purposes and not a bunch cheaper than the DPS's).
There's also the matter of boots; assume you already have AT boots or at least alpines with a walk mode, otherwise you will be in so much pain you won't want to ski down when you get there...