To play devil's advocate, I'd like to ask you how much your load for a typical trip weighs, including food and water. One way to get lots of weight off your back, if you haven't already, is to lighten the load by eliminating unnecessary stuff and getting the lightest version you can find of the rest.

Assuming you've already done that, I'll continue along the same contrarian vein: a lighter pack isn't necessarily a better pack for your problem. If you're trying to move weight effectively, a good, functional suspension is more important than minimal weight. I'm not trying to talk you out of a good ultralight pack - and your collection appears to contain several - but, just for the sake of argument, go try on an Osprey Atmos or Aura. Yes, they weigh four pounds, but the weight transfer and general comfort is stupendous, plus the trampoline suspension that keeps the frame off your back, might be worth the extra weight.

When you try them on, you'll be best served by taking the gear (again, including food and water) that you'd carry on a typical trip you'd take. Load it into the packs, and you won't have to guess and estimate whether the pack will carry better or worse than those sandbags the store will try to use. If it's a busy store, call ahead to find out when they're not real busy so you'll have time to get it right without disrupting their business. A good store will let you do this; if they won't, go somewhere else.

I've not had great pack-fitting experiences at REI. The training and expertise of their sales staff is ragged - today, you might get someone who really knows what they're doing; tomorrow, you might get an "expert" who's an expert, but with bikes, not packs. I've had better luck at small outfitters whose staff actually backpack - and I'll buy from them, even if I have to pay a few bucks more, simply because of that expertise.

Good luck. Chances are good that you'll be happiest with an ultralight pack, but try the Atmos/Aura; it really is an unusually functional pack.