It sounds like you would do fine with a 32-40 degree bag for most your 3 season hiking in the sierras and the PCT in Oregon-but its really a personal issue on how warm of a sleeper you are, metabolism, etc. If you go with a 40 degree bag pair it with an UL insulated jacket like the MOntbell UL Down Inner, BPL Coccon. Then you will have more versitility within your sleep system and a camp jacket for those colder mornings and evenings!
There are many lighter and more affordable packs out there to chose from. Check out the Mariposa by Gossamer Gear (3600ci, $125, 22,3 oz)Golite Jam 2 (3100ci,$124.95, 1 1b 10oz) Golite Pinnacle (4400ci, $119.98 on sale @ Prolite, 2lb. All numbers represent size M, and you will probably need a large so the weights will be slightly higher.
Good Luck, Have Fun, Travel Lite!