#3 - M&P Sport II
Smith and Wesson has been making these rifles and they have a good reputation. Even without the dust cover and forward assist on the first M&P15 Sport, it still functions very well and has proved to be reliable in many tests. I've previously owned the older Sport model, and if I was in the market for another basic AR, I wouldn't hesitate to buy the Sport II.
I've also seen and handled the Sport II at the gunshop. Good overall quality and feel. The Melonite finish on the barrel is a good alternative to chrome lining. For the price you are paying, the Smith and Wesson M&P15 Sport II is an excellent buy.