I have no idea what else may be contributing to what you're hearing, but your cables are definitely crap and at least a part of the problem. Speaker cables (and interconnects, and power cords) are not a rabbit hole. They are very straightforward- you try them out, you buy what works. It is only when you try and make sense of why - or worse, try and base your decisions on why - that you plummet headlong into the abyss. So take my advice: don't buy anything you haven't heard in your system, don't even audition anything based on anything other than listening impressions. Buy only what sounds good to you in your system. Stay a million miles away from anything even resembling a measurement. The only three instruments that matter are either side of your head and in-between.
In fact, not just cables. Stick with this for everything.
In fact, not just cables. Stick with this for everything.