Dear Jamiek: What make a balanced unit is not the interconect cables but that the electronic audio link ( item ) was/is designed in balanced way.
There are units that are fully balanced ( input to output ) where you need a balanced cable at the input and output ( not because it comes with XLR ), this means that the cable internal configuration and connection to its XLR termination connectors are true balanced.
There are other units that are a only output balanced design with unbalanced( RCA ) inputs.
So it is not the cable termination the one that tell you if it is balanced or not but the audio electronic item internal design.
One advantage on balanced designs is that noise/distortions canceled between the balanced design.
So you don't have any advantage if you use XLR connectors in a unbalanced audio elewctronic item because this item accept only unbalanced audio signals.
There are units that are fully balanced ( input to output ) where you need a balanced cable at the input and output ( not because it comes with XLR ), this means that the cable internal configuration and connection to its XLR termination connectors are true balanced.
There are other units that are a only output balanced design with unbalanced( RCA ) inputs.
So it is not the cable termination the one that tell you if it is balanced or not but the audio electronic item internal design.
One advantage on balanced designs is that noise/distortions canceled between the balanced design.
So you don't have any advantage if you use XLR connectors in a unbalanced audio elewctronic item because this item accept only unbalanced audio signals.