rletts,
I understand your concerns about wanting a second site system for your AR-15.
I have found that the EO Tech 512 pretty much fits the bill.
I use a 512 extensively on my AR-15's with a couple of applications.
Here's why:
1) You need accuracy. The 512 has a 1 MOA center dot framed by a 65 MOA outer circle.
(If you look into sites other that the EO Tech, you'll see that the vast majority of them have huge aiming dot....I don't know about you, but I prefer to see as much of my target as possible. The 1" dot at 100 yards is prescision.)
2) No paralax.
(If you put that dot on the target, no matter your shooting position, it will be spot on.)
3) Av. Magnifier.
(the 3x magnifier turns the EO Tech into another animal altogether. Longer more accurate shots can be made if you add the magnifier. If you don't need it, it flips out of your line of site in less than a second.)
4) It's QUICK to get a site picture!
I have even eude it when gunning out of a chopper on hard to hit coyotes for a depredation program. Here's some footage I shot that shows you what kind of conditions I have to deal with. The EO Tech is better suited for that action than anything else that has been tried.
Hope this helps some.
Barry