Right now if I were not doing SS, I'd go with a Geissele barrel over a DD or FN (Hodge, Noveske n4, etc).
Hodge/Icon/SOLGW Drive lock or Hodge SLock rail
Pick your G$ flavor trigger and run it with a Vltor A5H2/Green Springco.
It's hard to turn down G$ stuff on sale now, but if I had to pick a...