Heartsound Audio holostages wired into speakers and line level are probably my favorite tweaks. I've tried Bybee, Perfect Path, Synergistic Research devices, Shunyata, et cetera... but the Heartsound Audio is the most powerful of any of them, with a warm sound that doesn't overdo it. I've got Heartsound devices on my panel box, speakers, line level, room corners, on top of my speakers, source, router, router power supplies, server power supplies, transport, streamer/DAC, amps, power cords, power conditioners, and on side walls. Krissy is also one of the few women audiophiles that makes gear. She is obsessive and I think all she ever does is trial & error tests with different materials. Really nice gal too.