That'll be a great build! Last year I did much the same except got BCM's pencil profile LW midlength upper with BCM BCG (but not hammer forged barrel). With my stripped lower, DD LPK, BCM stock kit, MOE pistol grip and handguards, CTR stock, rear MBUS2 and Gunfighter charging handle I came in about the same as a Colt 6920. If I'd wanted carbine length gas I would have just got the 6920 but preferred the midlength BCM. Otherwise there's little difference between Colt and BCM. Both are excellent.