definitely go with 3 bottles. You can toss the first one after it's empty. I'd add a couple more gels. General rule of thumb is a gel every 45 mintues.They really do give you a boost, but once you start on them they're like crack, you gotta keep doing em.
Personally, I find bars hard to deal with in a race. Good thing about gels, is that you can get them open and down even when things are lighted up.