Re: Sight/scope for ar-15
+1 for staying away from cheap junk. It's just that, junk.
Eotech is a fine sight for up close and works OK at longer ranges, the reticle is terrible I think and grainy compared to say, an ACOG. With a bit of practice, you can be quite fast up close with an ACOG and for certain you have a huge advantage at range.
A leupold CQT 1-3x tactical scope is (big) a very nice optic for mostly up close work, about $800. 3/9 MOA dot and a large ring, it's fixed but also illuminates if desired with a single AA battery. If money is no problem, an Elcan Spectre is about the best sight that is manufactured IMO, 1-6x with a flip of a lever and a ACOG like reticle with illumination either reticle or just a dot. It's big, ugly and does it all. (and something like a $3k+ price tag)
Aimpoints are about $400-500 and serve very well at lesser rather than more range but if your battery runs dead and don't have another, your down to flip up sights as there's no reticle, just a dot.
"Loud noises don't end gunfights.... well placed shots do."