I agree with both - kinda. I think you can move the rock like JamesR described. I alo think that as you add coral, you'll be adding more rock anyway like Dragonforce described.
Thing is, you've got an opportunity to re-arrange with your coral in mind when you get it. Check out some of the coral at your LFS
and the rocks they're typically on. Now, look at your own aquascape and see if you've got ledges, or crevices, or otherwise space to put coral. So, as you re-do the rock, you can make space for new rock/coral.