@gladmo, I am not surprised at the increase in performance you achieved with your SVS sub. We are, after all, just listening to a modulated power supply.
Power Cables on Subwoofers do Matter
I read an opinion somewhere on this site that swapping the power cable on a subwoofer has a minimal effect and may not be worth it. I have a very different opinion. Power cables can completely transform a subwoofer’s performance.
I have an SVS SB-2000 powered sub and my preferred power cable, a Zavfino Fina, has made it sound like a different animal altogether. It has much more punch, freq response linearity, and liveliness. The manufacturer included power cable makes it sound slow, bloated, and almost out of tune just because it’s sloppy, in comparison. The only drawback to the Fina is that slam below 30-40 hz is a little recessed but it’s not major and is still clearly my choice. I also compared five other aftermarket power cables from other components in my system and they ALL had a different effect on the sub. For testing, I used various crossover points and most of the testing was with the loudspeakers off in order to isolate the sub for critical listening.
Cheers!