I agree Brad. The Osprey Aether 85 (lighter frame than the Argon) I carried on a long backcountry trip last summer with 50-60 pounds in it the entire time and never felt as if it was sagging. I would think the Argon could easily handle 80+ with the stiffer frame.
I'm talking Crescent, not Argon or Aether... the old Crescent is definitely stouter than the Argon, but the Argon seems like a decent compromise between the old Crescent frame and the Aether for sure...