I must be missing something - won't you simply be connecting a sub cable (RCA or XLR) to the line in on the back of the sub? Are you specifically planning to use the speaker level inputs?

I just looked at the manual for the EP800 online and it must be out of date as it does not show 4 sets of binding posts.

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1