DPMS's basic stuff is pretty light. Their Sportical/Oracle type rifles check in right around 6.5lbs.
I bought a Sportical a few years back when AR's were going nuts (early '09). Got is barely used, with a Millet Red Dot, a tac rifle case, couple extra mags, and about 900rds of PMC for $900. It's been a great rifle. A couple hickups with Silver Bear, zero issues with any brass ammo through a few thousand rounds. Subtract the ammo value, and I'm only into the gun and accessories for $600 or so. No complaints.
I've upgraded the Glacier guards to MOE for a tighter fit and BCG just for the heck of it. Those two upgrades mount to all of about $125. The stock BCG became a spare, and I'll have a cheap and light extra AR that has yet to ever fail me with brass ammo...and it runs about 95% on the Russian stuff. Maybe it won't be my go-to when zombies or aliens invade, but it'll be a competent backup at the very least. And a heckuva fun range toy.
"The Future is Unwritten"