Your experiment won't damage your equipment, however, I doubt it will reveal much about the cables. First, your listening room would have to be absolutely acoustically symetric. Second, you need to listen in mono. If you use a stereo source the speakers will not have the same input signal. Third, since you are only listening to mono, the cables stereo performance will not be revealed.
Hypothetical Question!
OK guys, help me out with this one! If you have one pair of monoblocks, a CD transport, DAC, and a preamp can you use a different speaker cable on the left (v.) right speaker (using the r/l balance knob of the preamp) to hear which cable you prefer? Will it damage any of the components? Would it work? Could it work with power cords? Thanks for your assistance.