If you stick with the Dayton driver I'd go no less than 4 of them. If you upgrade to SoundSplinter you might try 2 first and see what that gets you, it should be more displacement than 4 of the Daytons but I haven't calculated that so you'll need to verify. I have 4 of the SoundSplinters driven by a Behringer EP2500 and I can bring the house down if necessary and the drivers are barely getting worked out.
