[Russell Dawkins]

I just now heard of this logical-seeming device intended to improve the performance of monitor speakers, both stand mount and console mount.

I haven't heard it, but it does make sense intuitively and the pros on this page who are endorsing it are very experienced and, I'm sure, not easily led astray:

http://www.primacoustic.com/recoil-artists.htm

It seems to be basically a de-coupler that is big enough to be stable and adds mass in the form of a steel plate.
The bonus is it costs less than $100 a side.