The problem isn't the adjustment range on the sub, but the voltage level on the output on the receiver. Too high a + (it varies from model to model), and you run the risk of clipping (that is, having the voltage hit the max and hold there) during large LFE events when the receiver is also turned up loud.

If '0' consistently turns on your sub, then it is the best setting.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris