New power cord needed for speaker with powered subwoofer?

use  original . the best

Does anyone know if there is a difference in quality between Cullen and Morrow?

This should not even be a typical question. The answer is of course the bass will change with an aftermarket power cord. I do this continually with Legacy Audio XTREME XD Subs (reviewed). I wouldn't dream of using the manufacturer supplied dud cord for better LF.

Yep.  Like Nonoise above, every single component I have tried has been improved with the use of a suitable aftermarket power cord.  Not subtly, either.

My experience with Vandersteen Quatro's was that some Elrod Statements feeding their built in subwoofers brought worthwhile improvements in bass reach and tonality, and also brought better nuance and tonality well up into the midrange.  That surprised me.  The Quatro's come with a very heavy gauge OEM power cord, unlike many, but the aftermarket cords were definitely worth it for me.

@jbrrp1 Is it possible to boil it down to materials, gauge and manufacturing technique / innovations?.  The price for cables is all over the place. Just wondering if you can help. Thanks