[BR3W CITY]

Running a sub off a single channel of a 4-channel amp means your only delivering 1/4 of the amps RMA power to the sub. That amp is only going to deliver 75w at 4ohms to the sub, which is really low for a sub. You're more likely to blow the sub by underpowering it. You also won't have any ability to adjust the crossover, so your sending the high frequencies to the sub. It'll end up functioning like an underpowered PA speaker.