I do have my seat mounted on vibration dampers.
However, they are not mounted for the reason you may think.
Your question was phrased, "...To have the best effect..."
In that regard, I have to agree with Nephilim, that they may not be needed.
My setup has the Buttkicker mounted to a steel plate and rod mounted under the seat.
I tested my seat with and without dampers. I noticed no appreciable difference in effect.
So why did you use them?....you're asking.
My audio system is split into three sections.
The headphone audio, in the helmet...The speaker audio (2 speakers and a sub), in the cockpit....and the Buttkicker, on the seat.
Typically, I have all 3 on, at the same time. Loud in the cockpit. Enhanced by the Buttkicker. Kept close by the headphones.
In the daytime, this is ideal. However, at night I would switch off the cockpit audio and just use the helmet.
Without the dampers, I would also have to turn off the Buttkicker, as the vibrations transferred through the pit and into the rest of the house were VERY noticeable!
So the dampers equal late night fun, without pissing off the family.
Food for thought.