Subwoofer options for Klipsch La Scala

We are considering trying out a subwoofer in our system, which includes Klipsch La Scala horn speakers driven by a 7W SET amp. If we find a good pair of Klipschorns, the shy bass issue will be resolved that way. But in the meantime, I am seeking recommendations for appropriate subs that would mate well with the horns. I understand that you can't just pair them up indiscriminately, but I'm not sure where to begin. I've read through the Klipsch forums, and the recommendations seem to be whatever someone happens to be using at the time. In other words, they are all over the board.

Requirements are purely for 2-channel audio, so musicality is first priority over earthquake inducement. And I would like to stay under $750 if possible. I've owned the Adire Rava and thought it was quite good, but does it (or the Hsu, SVS) compete with say, a Velodyne or REL? Thank you all for the subterranean input.

Howard