There have been several links posted on here recently to S&W MP AR's for around $800. I'd much rather have that than a DPMS. If you are willing to piece the rifle together yourself, even if it is just mating up a complete lower with a complete upper you could have a better rifle for your money. I think if you did a search in this forum of the last couple months on "AR-15" you will get lots of results back that have links to better deals than what you are posting here.
BTW- If you are going to buy an upper that does not have a BCG do yourself a favor and don't go cheap on that one part,
www.bravocompanyusa.com has top of the line, MPI and HP tested BCG for $139.00 and is about as good as BCG get.