^^ Not to nitpick, but your example has the wrong buttstock.
OP, the correct flashhider would be the standard A2 birdcage, if you are looking to duplicate the M4. Somewhere on here I saw a picture of an extension that looked pretty good with the standard flash hider to make the barrel the requisite length.
As for the rail, the M4 comes standard with just plastic handguards, but most combat arms units have Knights Armament rails on them, the one you linked looks to be correct. I wouldn't sweat the brand personally, unless you want maximum authenticity. If that is the case, a 2012 to 13 model LE6920 SOCOM is exactly what I carried in the 82nd, except for the barrel length and not having Burst on the selector (which we virtually NEVER used anyway).
If you wanted to build it "right" you would also need either a Trijicon ACOG TA-31 or the M68 version of the Aimpoint Comp M2, a "KAC Broomstick" forward grip, a Surefire weaponlight at a minimum. We also had IR lasers, but I don't know how a person could justify that without also buying a rather expensive set of NVG's that would be required to even see the laser.
If I ever had a couple thousand bucks laying around I didn't need, I'd rebuild my old M4 that way. In the meantime, my PSA blem feels no different in hand than my old M4 did.