I agree with John. There is no reason to place anything between your receiver and your mains if your receiver has an LFE out.
Perhaps someone was referring to a more common practice of running a sub off of either the left or right main speaker because they have an older receiver that doesn't actually have have an LFE channel (Sub Out.) Therefore, all you can do is piggyback your sub off either the left or right front channels.
The EP500 supports this option with Line In and Line Out connectors but it's not necessary if you have a discreet LFE Out on your receiver.
