I would keep your existing crank-set & brifters, but go to a 12-32 Sram Apex ten speed cassette when riding hilly routes. You will need a new derailleur, like a Shimano Deore SGS and a new chain. This will give you a really huge range and the hills will take less out of you.

The spacing of some the gears is twice the change in cadence of your current cassette. If all your rides are hilly, the 12-32 is all you will need.

See the following thread, I've mixed the Sram Cassette with Ultegra Brifters and derailleur with great results: http://www.bikeforums.net/showthread...r-fear-no-hill