Why would you want balanced over RCA?
Unless you have long cable runs, what is the difference?
Some amps behave better when fed a balanced signal. For example Outlaw's multi-channel amps have a lower gain (and thus less noise) when using their XLR connectors. When running monoblocks, it does make sense to locate the amp as close to the speaker as possible (better damping), so one will have longer signal cables. Plus, well designed equipment will have the signal ground separate from the chassis (safety) ground (Axiom's subs do this when you remove the ground screw), which goes a long way in preventing ground loops.
Plus, XLR is just a more robust connector. RCA was never designed for external, component to component connections.
