Are you set on an AR or are you open to other similar .223 rifles? I had considered getting an AR and as I mentioned before I think Bushmaster is the way to go with that choice but I instead opted for their M-17S Bullpup. It fires .223, accepts all AR/M16 magazines, and in my opinion is much more comfortable to fire.
If you're not familiar with a bullpup or this particular model the trigger assembly is positioned about at the mid point of the firearm. All of the action, including the magazine feed, is behind the trigger assembly. This rifle is one of the most balanced I have ever handled. I have not had a single jam with several hundered rounds of expensive and cheap ammo put through it. It is accurate, comfortable, and above all a real blast to shoot at the range. I have let some buddies of mine try it out and everyone that has tried it seems as impressed as I am.
Just thought I would suggets an alternative. Either way you go, have fun with it.