For what it worth..... I would never buy a Ar15, I would build one. Pick the parts and put it together yourself. I've wasted more money over the years buying the stupid things and then building them from there. You also want to decide what it you will use it for, do you want a mid or full length gas system? how heavy will it be? What kind of trigger feel do you want? There are way to many options out there to just go buy one off the shelf unless you are going to just go plinking at which point I say buy a cheap one.
My Ar I use right now is a M&P lower,upper,chrome lined barrel and bolt. It has a ergo f93 pro stock, geissele s3g trigger, Samson evolution 15" hand guard, Mad lever,troy midievel muzzle brake, hogue grip and Troy fold down battle sights.
I use a variety of optics depending what I'm using it for at the time. The gun weighs just over 6.75 lbs and I can shoot it strong or weak side with one arm, I wanted a light weight rifle in case I was unable to use both arms... It is all high quality and I have never had and problems with it functioning.
I would highly recommend lots of time studying and building your own gun. Don't waste good money on a cookie cutter.