The difference between a trash amazon ethernet cable and a Audioquest Cinnamon is substantial.
The difference between a Cinnamon and a Diamond Audioquest on my rig is not so substantial (quite subtle actually).
Essentially, it comes down to the resolution of you room+rig (the pre-requisite), i.e., how nitpicky you want to be. To improve a room’s resolution, it costs a lot for treatments that actually work. But, the latter tends to trump any gains from the likes of cables by a lot.