the only reason you would use the high pass or left and right coaxial inputs is if you need a crossover frequency lower or higher than the ones you can choose in your receiver. If your receiver's LFE output has the correct crossover frequency just use the LFE output. If you use the left and right coaxials, the gain on the sub will go up, basically the same thing as turning the volume knob up a little. They may sound a little different if the crossover slopes are different from the sub and receiver. I say just connect it via LFE.