First 16 mph is a bit faster than my cruising speed on flat terrain, so to average that with stops is not bad at all.

However, if your reason for upgrading is as you stated, you need a road bike. However, what you want to ride over-rides comments by me or any other relatively anonymous forumite.

While there are things that a lighter bike will help with, like acceleration and climbing, if you are on relatively flat terrain when you are getting blown away, then there are 2 significant elements that are potentially allowing roadies to blow by...

1) Aerodynamics (this may be difficult to change with the relaxed geometry of hybrids, other than possibly full on flat bar road bikes).
2) Difference in fitness level.

1 can be accomplished on any bike with more saddle to bar drop, whether a new bike, or going from a riser bar and stem to a flat bar and negative rise stem

2 doesn't depend significantly on which bike you are riding.

There are minor improvements possible with rolling resistance as well, but the two above are the main factors for maintaining a high speed.

With your personal objectives, I would mix things up, like doing intervals etc. Doing something different than just riding hard can give you benefits. You might want to read for a while in the training forum, and see what performance cyclists do to increase speed, acceleration and endurance.

And, just to be clear... While I do believe the above are valid points. There is very little that can compete with a new bike related to motivating you toward whatever your goals are.