I guess technically you could, but you would just be playing either the left or right channel through both speakers. You can only connect either the left OR right RCA to the input on that EQ.* If all of your music is recorded in pure mono it wouldn't be a problem, but all music is going to be recorded with some sort of panning or phasic differences to present a soundstage.
*If you do decide to just run mono, make sure you only split
a signal using y-adapters. Never try to combine
a signal (like combining the L and R channels) with y-adapters.