Any super glue will work. S'long as it's a cyanoacrylate-based gel you'll be fine. I use Loctite super glue gel for most of the modifications to my live rock and coral mounting.
It depends on what you are mounting. I only use the superglue gel for mounting frags and small corals and the two part epoxy for mounting large corals and aquascaping. One stick of the two part epoxy can get quite a ways IMO. For an epoxy for alot of aquascaping I wouldnt use either of these products. If you read on page three of this thread there is a product described and pics of pillars and columns being built. http://www.reefs.org/phpBB2/viewtopic.p ... c&start=40
A two-part epoxy is just like it sounds. You mix both parts and apply. I've found they don't work well unless you can apply significant and constant pressure, hence why I use super glue.
However, I only work in nano reefs. I have a 10 Gal. and a 24 Gal. Nano Cube. So for my purposes I will never need epoxy.
I wouldn't glue rocks together. I took a note from sanjay as well and it would be better to drill and put in posts. Came out awesome and sturdy for me.
look at what sanjay did and I also put pictures on my thread in members tank specifications. where i show the drilling and all.