Power Cables on Subwoofers do Matter

Actually you are wrong.

Alternative current is actually a sinusoidal wave and it's not moving back and forth. 

It doesn't really matter what cable you are using for powering your amplifier: if it did then a 10.000 euro amplifier would be sold with a better cable than the generic one (let's say a 500 Euro cable). 

Power cable makes a difference?

The current is sourced from a transformer placed somewhere far away outside the building. Then it passes several long cables to the building main panel where is distributed through other cables to each apartment or whatever place. Then it goes in the home distribution panel and then to each plug. 

If someone is saying that the last 2 meters of cable can change the sound of a subwoofer while the current is passing through hundreds or thousands of meters of cables and hundreds of connectors + a few panels ... maybe they can explain us how !

I can understand that the RCA / XLR / or other cables placed between a sound source and final speaker can make a difference (if really bad cables are replaced with decent / cables) but the power cable can do absolutely nothing unless it is damaged or too thin. 

So, ... 

 I went to my local store to test a subwoofer and a dac. I know very well the salesman and we have a good relationship (he sometimes let me test at my home some equipment if they were returned / opened by a different buyer). 

After testing / speaking about DAC's I asked him about power cables and if he thinks they can make any difference especially for a subwoofer. 

They have lots of cables so It just happened I could test a Zavfino cable with a Monitor Audio subwoofer and an SVS. To my big surprise for both subwoofers it was a difference between the standard cable and Zavfino Fina. It was not a big difference but you could hear it definitely. I didn't expect that for sure and I was surprised by the outcome. 

Then he insisted me to test a more expensive cable: gigawatt powersync plus. He told me that out of all the cables they tried this was the best bang for the buck. Wow, this cable really made a difference: the bass was more tight, lower frequencies, deeper, even the stage seemed wider. Everything sounded so clear, like being a different subwoofer. I really can not understand how a cable can make such a difference but it did. He told me that there are even better cables but those are a few times more expensive and it would not be a bigger upgrade over this one. It appears they use it for demo with all their equipment so I ordered one because I didn't want to buy a used cable. 

When it arrives I will most likely test it with the dac I currently have and with the amplifier. I may end buying another one or two ...

So in conclusion: I guess I was wrong.

They have in the store more expensive cables. Some are 3X ... 4X the price.

I will do better. I will test myself. 

I have a local Hi Fi store that has lot's of equipment including very expensive power cables and I will test them.