If this great room is open to others, likely is covered in windows, and may even have high 10'+ ceilings, you really need to factor in room acoustics first! No system will offer the WOW you are hoping for when the sound ends up coming at you from every reflective surface.
Walk around your listening space and just give a strong, singular clap'. And listen to what happens to that clap. Does it echo? Does is decay (go quiet) too quickly? Or is there a delay at certain places where the sound reaches your ears at different times? This is the beginning to understanding room acoustics.
I suggest a different approach, and that is to start with a 2.1 system, perhaps with bookshelves that will eventually make their way to the rear channels. Why? It will tell you how your room is going to affect the sound.
Companies like GIK Acoustics can offer great advice on selecting room treatments, and you may realize that is something essential in your space. And I personally would rather figure that out with only a couple speakers, rather than a whole theater's worth and be completely underwhelmed! (and by staggering your purchases, you might be able to provide a larger budget ;-)
That said, if you are sold on the Hsu sub, I voted for EMP. SVSound would be a close second, only because I would recommend purchasing a complete SVS system. They can play well with any sub, but they really shine, as I am finding with their Ultra bookshelves, with their own subs!