What you guys are discussing is a little irrelevant to the op, although very thoughtful. What really matters is if the op is on the right track with his project, which is what I would like to here from him if he has any questions. Besides, the op unknowingly won the first part of his battle by not buying an inferior product and choosing a high quality dayton driver.
I'm not trying to criticize you guys but I guess I am, sorry. I just don't want the guy to get confused, and hope that he is able to properly build his enclosure so that he gets to take advantage of his driver
And I'm curious op, did you already buy your amp? Because in a sealed box the dayton hf 15 should be able to take a little more power and squeeze out some more spl. If not, the 250 watt will give considerable undistorted ourtput, but when you really want to crank it, the amp will probably reach it's limits and cause distortion before the driver does.