Which cable do you think is most important?

I would suggest that the next few dollars you spend are on fixing problems in your room instead of trying to improve your system with cables.

If you are going to go the cable route, make sure that you do BLIND A:B tests.....because in most cases, in a BLIND test, you will not be able to reliably tell the difference. If you do find a difference, it's not going to be clear if you are actually hearing purer sound...or sound that is biased towards what you like better (but your friends/wife/others may not).

That's my 2 cents....but you will spend $1000's on wires.

Note: If you are a concert violinist with perfect tone and you already have an acoustically perfect room, then cables may make a difference. For the other 99.999% of us, you will feel that the sound is better, but no one else will be able to tell the difference....and likely in a blind test, you couldn't either.

One problem with sound is that it is "in the eyes of the listener". One can change speakers, change cables, change the room and all, to some extent, change the sound that you hear. For the better or not is up to the listener and there is, and can not be, any standard.

Remember that unless you are listening to music played acoustically, you are listening to processed sound and you are adjusting the sound engineer's perception to your perception. It's a losing battle.....and unless you have a different sound system for each sound engineer, what sounds good for one may sound lousy for another mix.

Now if you tune your system for acoustic instruments, you may find that anything that's been processed sounds thin or too much bass or whatever. Also, keep in mind that very very few singers are recorded pure...they are almost always processed in some way.

If you accept the above, you will not spend a great deal of time and money looking for the "perfect" cable.