I've used a number of big load packs. My favorite is my McHale. I've carried loads over 100 pounds with that pack.

I wholeheartedly recommend Osprey packs.

Back when I was buying in the mid-90's, the Gregorys were good but I felt they were too hard in their backsheets, the Lowes weren't comfortable at all, and the Ospreys had seam blowout problems. Seems like the Gregorys are still good, the Ospreys have gotten better, don't know about the Lowes, the Arcteryx are new to the market but at least well made. Yes, Marmot bought the Dana brand and their designs, but Dana Gleason now has a new outfit, Mystery Ranch. Google them, look at their website; the designs there are essentially identical to the old Dana ones and I'm guessing still excellent quality, workmanship, materials, and comfort. I used my trusty Terraplane on Denali four times; no complaints at all. Picked up an Astralplane since that's what the Denali guides were using and someday expect to use it on Aconcagua. Tested them out with 60 lbs of sandbags in the local REI and the place in Keene Valley, NY for about an hour each; comfy!