At my LFS, they sell Marco rocks and another brandless base rock. They sell the marco rocks not a lot cheaper than live rocks (5 bucks a pound while they sell live rock for 6-8 bucks). Those rocks are beautiful. They make nice caverns. Lots of holes in it. Perfect to fit coral plugs. The brandless ones (1.75$/pound) are white too, are featureless on the out side, but when you break it, it's like honeycomb on the inside. I bought a few marcos, and lots of this brandless rocks. I'd have bought only live rock and a few marcos for the look if they didn't have those for the difference of price. I found cheaper base rock on the web, but shipping costs are ridiculous due to the weight. Use the rock you want. The bigger, lighter (porous) the better.
I'd buy 20-25 pounds of live rock, and 30-35 pound of base rock.