I bought a few from here and was happy. They seemed better then the DPMS ones I have used in the past. They claim they get the best from others. I don't know but they worked well. They also let you not get some parts if you are planning something different like a Giselle trigger.
The only brand I have consistently heard of being low quality is DPMS; I have one but havn't tried it yet.
I have used Stag with no issues and they go for about $5 more (about $66), and since it works I see no point in spending more than that on any brand lower parts kit.
Armalite, Daniel Defense, Rock River, are all good from what I read.