I use a pair of Rhythmiks and couldn't be happier. I've also heard great things about SVS from people that I trust. You're probably in good shape either way.
I always note that I use an Audyssey enabled pre-pro from Onkyo to integrate the subs, even tho this is a strictly 2 channel, audiophile type system. Speakers rotate between Merlin, Verity, Magnepan and (primarily) Ohm. Sources are QSonix and Cary digital, Acoustic Solid and Oracle analog. Down the fairway, audio hobbyist hardware.
I definitely prefer the "odd bedfellows" approach to a 2 channel system that includes subs. IME, whatever benefits were provided by my high end preamps (ARC LS-25 or Joule LA 100) were swamped by Audyssey.
The usual IMHO and YMMV disclaimers apply here.
Marty