I know amaranth is the stage after CHIM but what exactly is it???

From MK:

"To the close dreamers, don't forget the Amaranth. There *is* one step beyond CHIM, but you're right in that it is not godhood. It's the flowering of a statehood where the images you give birth to in your dream-- stolen (?) from first dreamer-- wakes up. Wails knowing free will. And begins to dream in the same way. Children of liberty without end, and then the music lives forever as a pirate radio tuned against the rules of Heaven and the vulgarities of Hell."

so they become godhead i dont get it???

They become a new godhead. CHIM is the realization of one's place in the Dreamer's Dream. Amaranth is when you escape the Dream and become your own Dreamer, within which other CHIMsters might develop.

It sounds to me like the person who reaches Amaranth is able to take the dreamer's imagined possibilities and make them into a thinking reality--or turning beings into gods serving under them--or something similar. It sounds like being at the head of the subgradient, the tip of the branching tree.

Edit: Ninja'd, and probably a good thing too. That explanation is much clearer than my guesswork, although I'm glad to see that I was at least on the right page.

It says it isn't godhood. More likely, you are simply able to dream things into being as well. I don't think you become the Godhead (we already all are, in a sense,) but you reach a state in which your dreams also become reality.

EDIT!: I will also say that there isn't much information on Amaranth, as it has yet to be achieved, to my knowledge. Neither Talos nor Vehk have acieved Amaranth, and i've not heard of anyone achieving it.