I have a MS309 and am V pleased with it. I have an aging Yahama sw60 before, so I don't have much to compare it with. Its in my converted cellar which is 15ft x 8ft. The frequencies go low enough for me and has enough slam. I ran the CD that you get against a SPL meter and tried to eliminate the boom as best I can. It has made a big difference overall, one scene for example is from Return of the King where the Battle for Minas Tirth and the elephunts, the bass is amazing.
This isnt a technical review but hopefully will help. But the best way is to hear it for yourself and review it against other subs as well.