Since the high-dollar crowd is throwing out their suggestions then you may as well add this one to the consideration list.
http://store.seekoutside.com/packs/I suppose the milsurp would certainly work, sounds like they're well made. I don't believe you need to drop $500-$600 for a decent pack that will work for you. Different things work for different folks.
Some apparently believe it's a crap pack if you don't spend 6 bills. Others get by for years and are perfectly happy with a $75-$150 LL Bean, REI, or Cabelas pack.
I took my first backpack hunt with a used Dana Design Terraplane I bought on ebay for cheap. It is a great pack and I still use it for backpacking. I've bought a like-new Eberlestock J-107 Dragonfly on ebay, used it on a backpack hunt last Fall then I sold it. Not a quality issue, just I didn't much like it for me. I've had a Kelty, and another Eberlestock and some daypacks.
I've ended up with the Paradox above and I believe it will be the last pack I buy as it has the features I want, is lightweight, more versatile than any pack I've used, and just a quality product. I believe it more than capable of hauling a moose, not that I likely ever will.
Anyway, my point is, it may take a few near misses and trying several packs to settle on what you want.
So far as my observations on here, it seems the Kifaru, Mystery Ranch, and Paradox lovers, truly love what they have and would not switch for any other pack.
