I am new to this and have done some looking.  I found good prices at the following places

Adco Firearms
I just bought a complete RRA upper 16" A3 for $375 shipped and insured.  He also has complet lowers with the A2 stock for $210 and $290 with th NM trigger.  I shot a guys AR-15 with the RRA NM trigger at my last shoot and it made all the difference in the world.  

CCMG
Complete DPMS lower with the ACE stocks from $280! These stocks are cool and lightweight.

Just hoping this thread could save someone a few bucks or help someone with a build.  Both sites have great customer service.  Just look around the board and you will see that.