You may want to look at Sportsman's Guide, they have a pretty good selection of packs. Their web address is www.sportsmansguide.com They have name brands as well as their own private brand of gear.
I bought one of their 85 liter packs a little over a year ago. I am very pleased with the size, quality, & features of this pack. Similar packs are running from $100.00 - $175.00, I paid $50.00 + S&H.
Another high quality pack that allows good organization and carrying comfort, although it is external frame, is the military LC-2 or ALICE pack. You can find them on line at some of the surplus stores for $50.00 & up. I prefer the large size over the medium.
Hope this helps.