I use a pair of IsoAcoustics ISO-L8R155 isolation stands under my Super 3XRS. The 3XRS are just at the top of the weight limit for these stands. I didn't want to get a taller or bigger stand so it wouldn't be bigger than the bottom side of the speaker. The stands do add a couple or three inches of height compared to being spiked to the floor. Where I bought them locally they were about $150.
I adjusted the tilt to approximate the tilt of the spikes but couldn't get it exactly the same. It's very close. I erred on the side of low because I listen from a legless floor couch.
My living room has wood flooring, not carpet, so my comments may not really be of use to the OP in his carpeted listening environment. I don't know how these would work on carpet with their rubberized flat feet. (I mean, I know you could put them there, it's just that they're not really anchored to anything floating around on the carpet rather than firmly on a wood or tile floor.)
On my wood floor, it does make a difference compared to spikes alone. The midrange is cleaner and clearer, the background is quieter, and the bass is tighter. It adds a noticeable amount of what you might call refinement. It's just better.
To echo what others have said, the thick 2 by 2.5m area rug I put in front of the speakers does make a bigger difference for less money.
Another reason I bought isolating stands was to keep some of the speaker vibration from going directly into my downstairs neighbours' ceiling. That's a benefit not to be overlooked for those of us in apartment situations.
My single very, very small reservation...is that they don't look quite as sleek and minimalistic on the ISO-L8R stands as they do on the spikes. But the stands are black, so the looks are not bad at all.
