Very cool man. I've actually got a coralife 125 in the basement I'm eventually going to use on a frag tank.
So the rock depends on how strategically you place it. I could have probably fit another at least 25lbs in mine, but I wanted the shelves and gaps so the fish could easily hide. I think 125lbs will probably be enough and, I mean, you can always add more or take some out.
I'd start with 125 and see how you feel. Keep water displacement in mind. If you fill your tank up to the tippy top with water then start adding rock the displaced water is going to need somewhere to go, especially with adding 125lbs of rock. When I did mine, I think i actually put rock in first, then filled it.