Re: List of ar15 kit suppliers?
Out of your list, I would say PSA would be who got my business.
BCM is highly recommended as well.
http://www.bravocompanyusa.com/
I built my ARs from bottom-feeder parts and I've had to do a LOT of work on them to get them as reliable as BCM or PSA are straight out the gate. One thing I consider a major point with the other guys is the fact that I've had to ream the chambers on ALL my 5.56-marked barrels (except my Colt) in order to bring them to TRUE 5.56 specs. Little hidden details like this can be a big setback at the most inopportune moments if you use it for, say, law enforcement.
On the flip side, all my tinkering with those pesky "less than milspec" ARs has taught me WAY MORE than I ever would have learned if I just put together all my guns and they worked flawlessly.
There's a difference in a hobby-level plinking/hunting gun and a pro-level combat weapon. If you are like ME and just enjoy messing with guns and your life will not depend on it, then probably any of the brands on your list will be sufficient. If you want trouble-free from the get-go then spend a little more for the PSA or BCM.
Also, need to get your order in soon before the parts all dry up from the panic buying.