Well im sure someone is gonna want to debate me here but you really dont need light to keep live rock living. Live rock is alive with many different forms of life and there is not much other than some decorative algae that is photosynthetic.
What makes live rock live.
Ammonia, Nitrite and Nitrate consuming bactera
Coraline algae (photosynthetic)
Small crustations commonly called "pods
Small worms (aka bristleworms)
Small crabs (occasionally)
Macro algae (photosynthetic)
Small coral fragments (occasionally)(photosynthetic)
For a tank that deep a single or even double normal output florecent bulb should basicly only be used for viewing the fish. Your not going to get much benifical light for photosynsis out of those bulbs at 2+' depth.
I would go for some short VHO
bulbs or some Power Compact florecents.
Of course your corner tank is ideal shape for a single MH
bulb with a few actinic florecents.