I think the 8.4 is the sweet spot in the range and if you like the color it comes in bonus for you then. Not to say the other models arnt worth the price increase for the better gear, but you may not notice the difference and then have some extra money for some accessories. Pedals, bag, speedo, ect.

I like the look of the 8.6 but I dont think I could justify the cost jump just for the color.