Two options not given here that I recommend much more highly than any of them for both price and quality are Palmetto State Armory and CDNN Sports.
Palmetto State Armory build kits are of the highest quality, and last April I built my first AR using a $39 Anderson Lower purchased from a gun show and a $419 PSA Freedom MOE upper with enhanced trigger group.
I now have a 3 gun style rilfe with 15” free float M-LOC handguard, Magpul MOE furniture, and a nickle-boron coated hammer/trigger assembly with zero creep and a very crisp 5 lb break.
Before settling on the PSA kit, I was looking at CDNN Sports for their kits. They are for the very budget minded, as their kits include in addition to complete upper assemblies, lower parts kits, and buttstock assemblies, a basic carrying case and one magazine, for as little as $349.
I’ve food luck with th quality from PSA, but the shipping is absolutely horrendous. I’ve experienced it taking weeks to receive products from them multiple times.
CDNN is ok but shoppers should be aware that they are “liquidators”.