Artemus_5, thanks for your response. My objective is exactly what you wrote: to “make the mains sound better.” I don’t want a sub to provide more bass per se. I’ll likely bring a REL home to see if it can live on my hardwood floors without rattling the joint.
Mapman, you ask a good question about the Auralex Subdude, the isolation platform I’ve been considering. I read the REL webpage to which Artemus linked. The Subdude has a depth of 1.75”, I believe. The REL guy said, “When you put it up, call it two inches on an isolation platform. You’re decoupling the sub from the floor and in many instances, it’s exactly the wrong thing to do.” I don’t know whether or not that .25” difference means that the sub is decoupled from the floor when on a Subdude.