You need a step bit like this:
grommets are the hard part, my tower was too thick for traditional grommets used for sheet metal and i had a hard time finding anything to work. I ended up finding funky faucet stop/grommets in the plumbing section and had make my own hole in the middle for the wires. They worked out pretty good, but they were a PITA to fit.
(Message edited by liquiddiet on January 28, 2010)