From what I've heard, people using limestone sometimes have a difficult time maintaining correct pH in their tank. I think your best bet is to buy some dry base rock and add some live rock to seed the rest. In my opinion, the shapes, porosity, and look of "holey rock" does not compare to the stuff you find in the ocean.
Making your own base rock is very cheap and easy, but can be time consuming (may take as much as two months to fully cure the rock before adding to your aquarium). People often post live rock for as little as $2/lb in the For Sale forum. The vast majority of successful marine aquariums depend on large amounts of biological filtration. It would be unwise to skimp on such an elementary thing. Nothing beats good, porous live rock that's loaded with bacteria-- your corals, fish, and wife will thank you.