Check out the 3-season 3-day list on bpl.com. Don't get worked about the brand/models listed and to a lesser extent don't get too worked up about the item weights. Use it to help you deside which items are "extra".
The list is fairly conservative in terms of item count, it is the specific weights that make it such a lightweight lists. If you end up with an item count (plus/minus 2-3 items) and a pack weight within 2-3# you've done all you can do without making expensive choices.
For example, the above list has sunglasses and sunscreen on it. You probably won't need those items on the AT. But you might want an extra shirt to sleep in. The list has a 32F bag that weighs 15.5oz. If your 20F bag weighs 3.5#, you can do much better.