I replaced the power cables to my SL3s with a dedicated Foundation Research LC1 power conditioner to each speaker, on the recommendation of Moon (the MLO member here, not the company). It made a big difference top to bottom. Note: it was not just a simple cable change.
One thing the change highlighted is that there is no real standard for IEC inlet connectors. The power connector at each speaker from the power conditioner does not fit the IEC inlet securely; it easily drops out. I have bought a couple of Furutech IEC connectors to replace the ones on the speakers as they do fit well; I just have to install them.