G.Skill Ares are generally low profile. what low profile is that the piece of hardware isnt tall or large( so that it doesnt interfere with another part of the computer). the reason why you keep ram low profile is to keep it away from the aftermarket heatsink, as heatsink fans usually hover over the farthest left ram slot.
ALSO, i would hold off from buying the pc for a tiny bit. NZXT is about to release their generation 2 NZXT Phantoms like next week.
what a desktop upgrade kit gives you is a 2.5 to 3.5 bracket holder(for cases without ssd brackets) and cables I think(if you ran out of the ones supplied by the motherboard you purchased) other than that, there is minimal differences.