what are you plans/ goals for the rifle? Are going to hump it through the woods? Is it going to be a target rifle? Those barrel lengths are fine, but a 16" with a shooter with capability is good for 800 yds, with less weight.
Also, the Knights rail uses a wrench that is proprietary, so you may have send it out to get mounted. Not a big deal but figured you may want to know.
I prefer Armalite for your parts kit, great springs, and a bolt catch second to none.
Geiselle trigger. Period.
My OBR uses a Lothar Walther barrel, LW50, I believe, and is 1/2 MOA or better with me shooting FGGM. I believe you can get it with a matched bolt, always a bonus. Also check out Criterion, a site sponsor, for a great barrel as well as JP and Rainier's Ultramatch