If you're wanting under $700 PSA is the only option for me. I wouldn't own anything else in that price range at this time. Reason, it's as simple as reading the specs, build material, and reviews from those who ACTUALLY know what an AR is capable of.
I personally would step up to the Spikes available through Aimsurplus.com for roughly $780. It's a quantum leap in quality over DPMS, Doublestar, BM, and so on.
It's sold out but is a good example of what you can get for a little extra money.
I linked a thread from another forum detailing the horrible findings of a local guy who works at Gander MNT. Academy. It's a climate controlled, clean environment ideal for proper functioning of a firearm yet some still show their true colors.