其實睇下樓主依家有乜同想做乜. 如果個source 係rca, 你用轉頭去xlr , connection us still unbalance. you won't take the benefit of balance (xlr) connection. so, don't think adding a converter will improve the sound. but surely, different connectors and how you connect the cable to the connectirs would impact the sound quality. but in short, if you change the rca connector from one end of the cable to xlr cinnector with the same grade, don't believe it would improve anything.
i have a pair of rca to xlr cable simply because the other end don't have enough rca connection, not because of sound better, if the source has xlr as well, i'll surely use xlr to xlr, that will surely sound better, if the system is true balance architecture.