You already own "costly XLR cables."
Try and obtain loaners of the cables you want to purchase through a dealer, friend, or The Cable Company, and then listen to them and compare directly with your current cables in your own system. If you really want to verify the value, have a friend randomly change the cables between your current cables and the new cables and then try to choose which you are listening to, or which you like better, without knowing/seeing which cable is in-place. Do that at least 10 times and if you cannot pick the same favorite at least 7 times out of 10, then don’t waste your money.