For many years I used a solid plywood base platform with 3 spikes that went through the carpet into a chipboard suspended floor. This was consistently superior with dramatic improvement in sound-staging and more precise bass to using the standard 4 spikes that didn't effectively pierce the carpet.
I tried StillPoints Ultra Fives under the speakers without the platform resting on the carpet. Besides being dangerously unstable under the relatively narrow 803, it was inferior compared to the spiked platform.
I then installed the StillPoints between the spiked platform and speakers. Obvious improvement in microdynamics, improved clarity from midrange and up, but no change to bass quality.
I then also replaced the spikes under the platform with the Townshend Seismic Pods. This did reduce the bass boominess a bit and resulted in a bit more bass articulation, with minor softening of bass impact. I think it also may have improved clarity in midrange, but I can't conclusively confirm without further comparisons.
The combination of Seismic Pods and Ultra Fives made a significant improvement in overall clarity, and more importantly listening engagement.
Seismic Pods are diametrically opposed to spiking where the intent is to ground the speaker to the floor to minimise movement of the speaker. With the Seismic Pods the speakers wobble back and forth if touched, but surprisingly the sound-staging is not worse, and if anything is a bit more independent of the speakers.
I cannot say conclusively whether StillPoints or Townshend is better for a particular situation.
To put the improvements in perspective, optimal positioning of the speakers in the room has MUCH greater impact on overall sound quality than any isolation.