As long as you get a reputable pack -- like Granite Gear or Ostrom, you'll be fine!  I would recommend against Duluth Packs....unless you like the retro look and feel of canvass, leather, and weight. 

I'd recommend you get a pack with a hip belt.  I'd also recommend you look into getting a waterproof pack, like a SeaLine.  If I were starting over, I'd research these waterproof packs.  I currently have Granite Gear packs, and I line them with heavy duty black plastic liners.  It would be nice to not have to do that.  I don't know much about these waterproof packs, such as wearability and weight, but they intrigue me.

The other consideration I'd offer: however big a pack you get, you'll invariably fill it!  So you might consider the future of your knees, legs, and back...because you'll need your component parts to be in great shape as you age and continue to lug these monster loads across portages! 

Good luck!

prouboy