Criterion, FN, Ballistic Advantage, Krieger and of course PSA / DC Machine, have all worked for me... just be sure it is a DPMS threaded barrel nut.
All my PSA's have responded very well to lapping the upper receiver face flat, and Loctiting the barrel in place.... I strongly suggest doing this... the improvements in precision are worth the added cost of a $30 lapping tool and some 609 / 620 Loctite...
DO NOT use the cheap Wheeler version... The Wheeler version is WAY to loose / sloppy a fit in my various Large Frame AR uppers >>> I bought a Wheeler just to see and The Pacific Tool and Gauge version is the way to go....( I now use the Wheeler ones to polish buffer tube interiors, smooths them right up... Lol )
PTG version...
http://pacifictoolandgauge.com/ar-tools/10318-ar-15-upper-receiver-lapping-tool.html
IT is worth the wait .... my precision improved dramatically.
My profile photo is from a TnG'd ( Trued and Glued ) PSA upper w/ Criterion barrel..
And here is a FN barrel with the same "treatment"... also 10rds 100yards.. Horn AG 155gr .308