The optic on the MSAR in my avatar is also the optic I use on my AR. It's a 200-buck ACOG clone we got in stock at the gun shop I used to work at outside Charlotte. A lot of our clientele was blue-collar farm boys who wanted the Mil-spec look but couldn't afford several hundred bucks for a good optic. It's not illuminated, it's not Trijicon quality, but for an inexpensive optic it actually shoots very well.
Check it out near the top of this page: Kingdom Arms
I'd like eventually to replace it with a REAL honest-to-God ACOG or other good, combat-proven optic but the bills right now won't allow it, especially when I'm trying to build a stockpile of ammo after switching from a .40 pistol to a .45.