The cables in the burly kits are too long.. go with a smaller size than what it says. The 16 kit will easily have enough slack for the 18" bars.. but I'd either go with the burly 14" or measure how much extra you actually need over the stock cables and ask them for a measurement on the cables in their 12" kit. They really are much longer than what they should be for what they list them to fit.
I'm with them I have 14" bars and the 14" burly cable kit is too long. But if your planing on going to 18" bars, why not just put them on? I would not want to spend all the time putting the wires in the bars only to do it again later.
As for road 6 bars, I love the looks and ride I get from them.