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) AVR is older...and only has Pro logic 2..via optical or coxial does have a sub pre out fixed at 80hz which is questions...should I utilize this connection or speaker in/out connections which typically hi pass at would either of these alter 2 channel or 5.1 listening...thanks for the feedback
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Bob always has good answers and I agree. Still, if it were me I'd pop for a new $200-$300 receiver simply to enjoy the modern setup, room correction, HDMI, and the superior surround effect that it all offers.