I've got a Burris. 1-4 on one of my Ar's, paid 200$for it in Cabela's bargaincave, one of the best optics I've run on an AR. On 1x it's like using a red dot, on 4x it's very clear, and has holdovers for standard 5.56 cartridges, out to 600 yds.
On the same gun I am running a set of 45deg backup irons ipaidless them 20$ for through amazon. They aren't as flashy as the high end stuff, but I've taken em out to 250yds on steel, and have had em 2.5 years now,through 2 different uppers. No reason to spend big line on back up irons if your life ain't on the line.