Gesundheit!
I guess I should buck the apparent trend of totally irrelevant posts and say that IMHO, HSU offers the best value.
SVS is good if you absolutely want to hear them before you risk losing any money and they are usually a little more finished looking than HSU (if you take off the perforated metal grill (that SVS generally does not show in their photos)!
For value, HSU is very good, but keep an eye out for discounts on Outlaw or Monolith subs since we are entering November - I would research the Outlaw and Monolith subs so you know what would work for your situation. Generally we never see much discount on SVS or HSU (or Rythmik or PSA) mainstream products, but Monolith and Outlaw are fully competitive subs that sometimes see deep discounts. I got my two Outlaw X-13 Ultras for $1,000 ea. (normally ~$1600/ea.)