Sat, another point of terminology is that there are actually no "RCA cables"(despite labeling), since "RCA" is the name of the plug at the ends, not the cable itself. Sometimes the term is applied rather imprecisely to a cable that isn't of the 75ohm impedance suggested for most digital connections.

As I pointed out in the reply to Mike Drew's thread, the cable itself can't make a connection balanced, and in your case both subs are operating with an unbalanced connection, despite the difference in the form of the cables. In a true balanced connection the receiver or separate pre-amplifier has to be able to output two voltages instead of one, with the second voltage being of opposite polarity. These two voltages then ride along the two center conductors(compared to one in a coaxial cable)into the amplifier. If any external interference hits the two conductors it would be nearly equal in amplitude if they're close together and would be of the same polarity. If the amplifier has balanced circuitry, it reverses the polarity on one of the conductors so that the two original signals are again of the same polarity and their voltages add, which doubling of voltage is an increase of 6dB(rather than the 3dB in a doubling of power). The noise voltages however are now of opposite polarity and tend to cancel each other, which is why a true balanced connection has greater interference rejection. If the gain on the balanced circuit in the amplifier was the same as that on its unbalanced circuit the balanced input would result in a 6dB louder level. To compensate and equalize the levels, the gain in the balanced circuitry is typically set 6dB lower. Sometimes if this compensation isn't made, or isn't fully made, the louder result on the balanced input will give the misimpression that it's of higher quality, although it's actually just a volume difference.

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Enjoy the music, not the equipment.