if you were to buy a sub with hi level inputs and outputs, that would be ideal (and simple) in your case, but the EP350 only has hi level inputs.
He's just use a pair of speaker wires from each of the output terminals on the receiver (Y-ing to split is OK, it's Y-ing to combine that's the issue). Run one set of high level outputs to the sub, set the sub's low-pass filter ("crossover") to 80 Hz, and then run the second set of wires to the speakers. Their natural roll off will blend in with the sub's filter.
There's not much one can do with a receiver that has no in built provisions for a sub-woofer.
