Another alternative, less expensive, that works very well for me in the big hills here in Eastern Washington is to replace your cassette and rear der with a Shimano MTB cassette (12-32) and XT derailluer. It works perfectly with my Dura-Ace everything else and, if I want, it can be switched back to the Dura-Ace der and cassette easily. The only downside is that the gear ratios are a little wide in the three large cogs, but when you need a bail-out and aren't willing to sacrifice your knees, it's perfect.