Adjusting your speaker placement, and adding some room tuning tweaks will do more to tame system brightness than wire, IMO.
The root cause is the synergy between your speakers and electronics. The problem won't be truly fixed until one or the other is addressed. Wire will provide a quick bandaide by masking problems elsewhere but it won't solve the problem.
That's why I suggest tweaking your speaker placement (which you have already discovered works), and adding some room treatments that will be useful no matter what gear or speakers you own, and will cost less than good wire.
The root cause is the synergy between your speakers and electronics. The problem won't be truly fixed until one or the other is addressed. Wire will provide a quick bandaide by masking problems elsewhere but it won't solve the problem.
That's why I suggest tweaking your speaker placement (which you have already discovered works), and adding some room treatments that will be useful no matter what gear or speakers you own, and will cost less than good wire.