If you don't mind NEA upper lower and rail then SFRC got some really good deals. I would get barrel and BCG etc critical components from places like CTC. For the rest like gas tube, gas block, pins, springs etc etc I get all of them from TNA. Have that said, I built a full upper with everything bought from TNA (CNA barrel instead of NEA) except BCG which is Stag Arms bought from ArmsEast, not an issue at all so far. All store mentioned above are site sponsors.