Almost any power cord upgrade is going to improve bass over the stock cord. I think that's a given, but sometimes the bass is bloated and sometimes it's tight. Same with the treble. I think different metals in the cable, and especially the connectors, have a big effect on that. In general, here's what I found.
tin plated brass connectors - OK, not the best but better than stock. You will get more, but not necessarily "good" more
copper connectors - this is usually the go-to for most people. It is balanced and can have fine nuance in both the top and bottom ends without becoming tinny or hard, it can certainly sound warmer than other options
gold plated copper - usually helps to smooth out the highs and tighten the bottom a bit more than plain copper, and it is a more solid metal and less prone to bending
rose gold over copper - same as above but with a bit more bloom on the rose, warmer than plain gold
silver connectors - this will definitely open up the top end, sometimes too much. The bottom may sound leaner than copper but it is also much tighter. If your system sounds bloated normally you might want to go here, but if it is already transparent this is too much of a good thing
rhodium connectors - these act like a loudness filter, extending both top and bottom and making them tighter, but it can also be too much of a good thing, except on a subwoofer (meow)
Just what I found in my system. Of course, trying these on a CD player might result in different results than on an amp, or a preamp. It's all about tuning the flavor of an individual component.