Most Beneficial Cable Upgrade

at the very least step up the quality on every cable first.

I would recommend something like VH DIY PC and Morrow or Signal or Blue Jean ICs and speaker wire.

In other words do not get ICs and speaker wire but ignore the PCs, there is too much to be gained from good PCs.

There is a big step up with the initial move up from stock cables in every location.

fwiw in case you have not considered this...

my first experience with power cords is when I replaced stock cords with DIY VenHaus cords, the soundfield opened up a tremendous amount and definition improved across the board.

a huge improvement for $65.00 each!