Your current bike doesn't look that heavy or inefficient to me, though if it's not a good fit, properly adjusted, and well maintained that could make a bit of a difference. What I'm saying is, don't expect getting on an ideal bike to suddenly give you wings compared to your current mount. You should expect only an incremental difference.
22 miles is a decent length round trip; drop bars will help with that if you ride on the drops to reduce wind resistance.
Your bike is already the right genre for your needs. I would pass on a mixte frame myself, but that's a detail. You might consider using your current bike as a learning platform, to optimize for your needs up to the point where you can accurately identify its limitations and thereby choose your next commuter bike very wisely. If you come on over to the C&V forum http://www.bikeforums.net/forumdispl...c-amp-Vintage? with your questions on how to tune up and optimize your bike, you will get some very helpful information, I think.