I can't speak exactly for the 5650's, but I installed 4 CDT-5800-II's a couple of months ago in my den. I followed the template, and thought it was a good fit. They "dropped" right in. When tightened, the dog ears (the little plastic "wings") swing out and keep them in place very snugly. The only thing was that one of them had no sound when I was done, so I had to pull it back out to check the wiring. That was kind of a pain. Not terrible, but it took a few minutes, because the ears kept swinging back out a little and catching the edge of the drywall. I would say Klipsch designs them to be a little loose, in the event you need to pull them out of the ceiling.
That being said, if you're the least bit unsure, I'd err on the side of caution and cut a little smaller. Trace out the template, cut maybe 1/4 of an inch inside of the line and see how it fits. You can easily scrape off a little more drywall if it's too small. Patching a hole that's too big, not so easy.
Good luck with your install!
