I used a Blast 26 (which I believe Joe has now termed the 30) for my CDT hike. Marmot sleeping bag, hexamid, 0.9 liter pot, jacket/puffy/extra LS shirt/windshirt at the most. It was plenty big to hold my gear and up to 7 days food. I had the standard mesh back pocket, water bottle side pockets, one mesh side pocket above the water bottles (for smalls stuff, headlamp, sunscreen, snack, etc) and one shoulder pocket (camera). I carried my Zrest below the mesh pocket with some thin line I added in two loops.
The gear you've described is similar to mine, so I think the 30 would work great for you. I didn't feel that I needed stays in mine, and I don't really put weight on the hipbelt, just use it for stability. The pack is uncomfortable with more than 4 days of food, but not unbearable. You may be able to use the smaller version for the AT, as you will probably never have to carry as much food as I did on the CDT, and you will never have to carry a bear canister.