HI I just got a memphis bella 5 channel amp but I see that it has only one sub input so what I want to know is do I use a Y rca plug and go two outputs non fading outputs from the d3 to the amps one sub input or do I just use one sub output from the d3 if so left or right or does it matter thanks any help would be great

Just hook one of them up. Either is fine, left and right doesn't really matter in the case of a subwoofer.