I did the same thing several years ago and have never looked back. My Burgman only had 5000 miles on it when I decided that I needed something bigger. That and I got really tired of the crappy suspension on the Burgman. You'll notice the difference right away. While the c14 is only about 150lbs heavier, it rides like a Cadillac compared to the Burger. The seat is also Much more comfortable and because you actually have a tank between your legs, you can use your body to help stabilize your riding position. The Burgman was/is a good commuter bike, but as soon as you want to do some more serious riding, you'll have to step up. Just my opinion, of course, but at 6'2" and 250lbs, the little Burgman was just not going to cut it for me on a 4500 mile trip. And yes, I rode to Sturgis from Atlanta (and back) on the Connie and would do it again tomorrow without changing anything.
The Connie's gas mileage around town is far worse than the Burgman, but I can still get 38-40 mpg around town if I hold it down. But, what fun would that be? The Connie can get 50mpg out on the open road and that's good enough for me. I think the best mileage I clocked on the Burgman was 65mpg on the open road.
You won't regret the change. Yes the Connie is heavier at low speeds, so what. Give it a day and you'll be flipping it around like a dirt bike anyway. At speed the Connie is an absolute joy and handles extremely well. The Burgman is a fun bike, but it just does not compare to the Connie.
Have fun.
Cheers
--Corey