I've been thinking about going compact on my bike, but it's still pretty new to me. Right now I have a 39 in the front with a 25 in the back. The difference between my commuter which has a 32 in the rear has been pretty substantial these first weeks, but I think I'll give it more time.
I'd say go with a compact crank and keep your cassette if you decide to change, but I think it's a good idea to do what J Turk said, and try it out first. It might work.