When looking at wattage, the only way to compare is if all things within the sub are equal....different configurations, electronics, and drivers have different efficiencies.

That said, if all things are equal, to get a 3dB increase in SPL, you have to effectively double wattage.

On top of all that, at normal listening levels, you can not assume that the subs sound the same.

At 4000cu. ft., all the subs mentioned should be able to handle the room. Also remember, Hsu has a Canadian distributor.