You will be hard pressed to find a better value in an upper assembly/rifle kit over PSA, especially when you get into their "premium"/chf line of barrels. Those are made by FN, who is a supplier to our armed services, and are found in "big name/high end" uppers. I promise I don't work for them, lol. I just have been researching suppliers for several weeks, and keep ending up back on them.
If this is going to be a range toy that will only see a few rounds occasionally, AND you are not relying on it for defense of life, you pretty much would be okay with anything. If you plan on using it frequently, OR for self defense, you should consider looking into their "premium" uppers. JMO (based on incessant OCD research, lol).
Would like to see your final product. Good luck with it!
PS: That AIM bcg linked above is a nice alternative to the NiB if you prefer the "stealth look".