I was reading the thread about Looking for an AR and all the comments about the quality of different lowers. In case you don't know, there are only a few people making lowers and they SELL them to all the others. Here is link to a list of who makes who's lowers. It is a few years old so might not be current but otherwise useful info.
List showing ACTUAL makers of lowers and who they sell to : AR-Series Rifles
List showing ACTUAL makers of lowers and who they sell to : AR-Series Rifles