Well all of this depends on how loud you listen placement in the room....carpet vs. hard floors and MANY other factors. The room you stated is a medium size space, but as for the subs you recommended I would strongly suggest you look to SVS and HSU instead. These are both internet direct companies that will give you a product at similar price points that will blow these two ot of the water....
What was your max budget for the sub and then we can give some more ideas as to what to consider....