Well guys, unfortunately some unexpected car repairs have set me back ~2 months on my AR budget, so no new upper for a little while. I do have to say the responses I got were very helpful, and my plan will be to go with a 16" barrel. Here are my reasons:
1. I have realized that going out beyond 500 yards will be extremely rare. If I choose to shoot longer I will be moving to a bigger cartridge, at least a .243, but probably something like .260 rem or .308.
2. I have ruled out a 20" barrel. Just more length and weight than I want. I am only using this future gun to shoot for fun, no hunting or SHTF where I need to worry about velocity and KE for effective killing/stopping.
3. I really only gain ~30-40 yards with an 18" barrel over a 16" barrel. I value the ability to carry the rifle due to lighter weight more than the 30-40 yards I will gain.
4. I do not want a pinned muzzle device that would be required with a 14.5" barrel. I prefer my first stamp to be for a 5.56 suppressor.
I will be using either BCM or Rainier for the upper, these two companies seem to be the best fit for me.
There is nothing wrong with any of the lengths or products suggested in this thread, and I appreciate the variety of responses I received. I also appreciate the photos posted, nice sticks! Thanks everyone!