I have a 2001 LeMond Zurich with Ultegra 9-speed. The crankset is 53-39 and I'd like to get some better climbing gears. Will the current Ultegra 10-speed crankset and external bearing BB fit ok? Do I need to use a 10-spd chain? Also, is it worth the extra $ to buy a 12-27 cassette to use instead of my current 12-25--would 2 lower teeth make a diff worth it? Thanks.