the cc plates allow you to drop your ride and keep the alignment, plus reduce the camber wear on your tires that happens when your tires is either more worn on the inside or outside due to being dropped too low. The subframe connectors stiffen ur ride, they make it so ur car has less body roll or flex when u take turns hard and stuff like that.
oh yeah, ur heads, comp cams and longtubes sound like a pretty nice set up, what kinda power gains do u expect?
and as far as spending ur money, id def go with suspension to get that power to the ground