Well, boxing day is coming and I know there will be some deals out there. Two years ago I got my first Velodyne DLS-5000r on BD and my second last year, at BD too. I got them both for 599$, which makes it a pretty good quality/price ratio.
SVS, HSU and Velodyne (on sales) makes good sub. Never heard the SVS though, but 9 out 10 persons here tell that they're awesome.
The HSU VTF-3 MKIII is a wonderful sound, extremly soft and precise bass reproduction. The down side of this sub is that it may lack a little bit of power in some situation, and may ear some port noise (turns me off completely).
The Velodyne is a beast. Brutal power but very musical and clean at the same time. I never turn them over 50% cause I fell too much pressure on my ears. The drum kicks that come out of them are insane and very good with jazz and classical musci too.
Hope this could help you!