I currently have an Aimpoint CompC on my AR, but I just had a strange thought that maybe I should sell it and use straight iron sights on my rifle to free up some cash for other rifle accessories.  And with the objective of purchasing another scope, perhaps an ACOG, later on.

My AR is a flat top and the gas block is railed and without a front sight.  

So, if I sell my CompC, I'm going to need a complete set of iron sights.  

What is the best thing going out there for iron sights?

Troy front and rear flip sights are without question the best flip sights. For fixed clamp ons, get a LaRue rear and an LMT front (rail handguard mount) or an RRA or similar front and clamp it to the gas block.

Armalite has been producing the gas block attatchable front sight a long time. LMT as mentioned sells one now. GG&G makes a folder which is a mechanical marvel compared to the others. You may not need a folder. Of these they all use standard sight posts/small parts and that is important. There is a choice of sight posts which use this most used system.
GGG SIGHT;