I've ridden Ultegra 6400 8 speed and 6500 9 speed, personally I like the 6400 8 speed more, it is my favorite Shimano group. 6500 performs wonderfully as does the rest of the Ultegra series. I like 6400 more due to its look and feel, 6500 and 6600 hurt my hands. So if you like it and it fits I would go for it, 9 speed is wonderful.