I used a Nimbus under my previous turntables to good effect. The improvement with the SOTA Cosmos, admittedly rather heavy for the Nimbus, was good, while the improvement with the Linn Sondek was stunning. I don't have experience with the Promethean, although it can take a lot more weight depending upon the springs used, so it's definitely worth a try. Microseismic very low frequency vibration is effectively dealt with on these devices. I use a Nimbus under my CD transport and wouldn't be without it.
Brian
Brian