What makes the biggest difference in sound quality?

That’s a very long cumbersome way to express your belief that cables have zero impact to the performance of any audio system. And since you are also of the belief that “we hear what we want to hear”, I take it you never tried (as in listen) for yourself? 

I still have to pick my jaw up off the floor after installing Duelund Bypass capacitors to my crossover

@yuviarora - yep! me too

When you can get risk of the noises everything become dead quet all you hear was pure musical presentation!

The headline itself doesn't mention pre or power amps. So, overall, what makes the most difference to a system is the source. If we talk about items mentioned below the headline then it's interconnect cables.

This is based entirely on the fact that once musical detail is lost or otherwise distorted it cannot be retrieved further down the line.