More dumb sub set questions...5.1

Humour me folks...I am currently setting up a NHT sytem(4 superzeros, cc, and sub yet to be named)...my AVR is older...and only has Pro logic 2..via optical or coxial connection...it does have a sub pre out fixed at 80hz which is non-defeatable...my questions...should I utilize this connection or speaker in/out connections which typically hi pass at 100hz...how would either of these alter 2 channel or 5.1 listening...thanks for the feedback