Where are you located? 3 seasons or 4 seasons? How much do you want to spend?

For your sleeping bag, you can get a good, basic, 20* down bag from Campmor for about $119. If you Google a coupon code for Campmor, you might find yourself with a 10% or 20% discount. Campmor 20* Down Mummy That will save you around 4 lbs of pack weight right there.

You can buy used 3 season tents for extra cheap, or if you'd prefer new or some specific design or style, there's a lot of websites running good sales right now, including Moosejaw. Sierra Trading Post also has good deals on gear, also check Spadout and GearTrade. With your tent weighing that much, you can easily shave 4 more lbs off.

I'd upgrade your sleeping bag and your tent before I'd upgrade your bag. You said your only major complaint is sore shoulders. This could be alleviated by a lighter weight bag and a lighter weight tent. You may find the pack being perfectly manageable with the lower weight, and your pockets won't be hit too hard either.