This is just one man’s view:
Since you’re describing a 1600 ci stuffed bag, that reminds me of our scouts. These Kelty bags can handle the abuse of scouts. But let me digress first:

Background: most of us here have internal or no-frame backpacks whose MAIN compartments hold 2000-3500 ci, and weigh 0.5-2.5 lbs.

Your sleeping bag will fill half the volume and thus not leave you much left. Typically, these sleeping bags will invite their 6 lb tent along (It’s funny how these two are always pals)-- which will take up more weight and room.

Now some store clerk will say “You want this $250 North Face internal frame pack because that’s the most popular and will hold all your stuff”. But you find out that it weighs 7lb for a 5000ci volume. Those 3 items alone will weigh 18lbs.

To help keep costs down and weight down for our scouts, there is nothing wrong with an EXTERNAL frame pack. The pack need not weigh more than 4.5 lbs. ( http://www.campmor.com/outdoor/gear/Product___60307 weighs 3.7 lbs, $50). The scouts lash their BIG bags outside on the external frame. However, these are double bagged with two trash compactor bags (2mil x2 thickness) so they can handle trail abuse. The scouts have car-camping tents and backpacking tents. On the hiking trips they take the backpacking tents (Kelty Teton 2, 4.6 lbs). So initially our scouts big 3 will weigh 13lbs. We have also trained them to use alcohol stoves (and don’t use scout mess kits)--- another big weight savings!

Eventually, the scouts will work and raise money to buy themselves a climashield bag so it will weigh less and compress smaller. My sons/daughters have down bags and have been trained in respecting down.

Find some trail and test out your stuff. Maybe do an overnighter 2-3 miles from your car. It gets addictive after that…

-Barry