I feel that there are a lot of reasonable choices near your price range.
You really need to know someone how knows ARs and have them look at the rifles you are considering.
I own and operate an AR company, and read on as i continue to plug someone else.....
Can there be problems with a DPMS? yes.
Can there be problems with a RRA? yes.
Can there be problems with a Larue, DD, Trident, LMT, Les Baer? gulp...... but yes. (though i hope they are few and far between)
What you need to do is have someone look at the particular rifle you are looking at.... hold it...
look for finish chips, wear marks, did the guy putting in the roll pins know what he was doing, or did he scrape up the finish?
how is one trigger compared to the next?
are the safetys crunchy, or smooth and camming?
how does the upper fit the lower, is there too much slop?
do the pins fit tightly between the upper and lower?
is the stock correctly alligned to the receiver?
Here we build a lot of rifles, but no two look EXACTLY the same, and even though we hand hone our triggers, no two are exactly the same, you need to look at the individuals not the groups.
i do however reccommend you buy the absolute best you can get... that doesnt mean brand.... that means individual rifle.
have a good 'un
-j