I agree with Shady and Pogre's posts, with the one exception that I would discourage you from the SVS subwoofer!
I am not a fan of subwoofers that do not have good tuning flexibility!
The SVS PB-2000 has no tuning options! You are in a town home and I will assume there are only so many locations for a sub in your room that would be feasible (and/or have acceptable WAF). You were not specific about which Hsu model you are considering, but they almost always offer tuning in the form of:
1) Plugging one or two ports
2) Switch between two EQ profiles
3) Variable Q knob
For setup, I would
1) determine where in your room you are willing to place your sub (I assume, like most people, you are not willing to put you sub in the middle of where a person would walk through the room)
2) Perform a sub crawl of those locations to determine which works best
3) Locate the sub there, then use the three variables above (along with advice from Hsu) to get the best sound at you listening position.
4) Let Audyssey make adjustments as the final step! Several accounts have shown that the best results are obtained when everything else is optimized before you run Audyssey.
Not part of the sub setup, but I also would recommend you get the D&M Audyssey app and compare the results for "full range Audyssey" vs "Audyssey limited to below 300Hz"