I really do enjoy this website. Great pics, guys.
My main listening room is 33' x 14' x 9', open to a 18' x 4' x 16' foyer. So I'm talking around 5310 cu/ft to fill with bass. The SVS Plus/2 does well, but I may be upgrading to dual Ultra 13's if SVS allows a "trade up" plan.
I would consider your main living room for your system. You'll use it more for every type of viewing, whereas if you put it in the basement, you'll probably only dedicate it to movies. With the new LCD's, you don't have to worry about how bright a room is. My 37" is awesome with all the sunlight. Saturday afternoon sports is so much better with my LCD compared to my Toshiba 36" CRT. No glare!
You can always put a second "home theater" system in the basement, but IMO you'll get more use out of your upstairs setup. The HSU should do the trick upstairs for a much better price. You could always add a turbo if bass is lacking, which I'm sure it won't be.