powered subwoofer

I have a passive system that has a powered mixer with the system, and has multiple channels, inputs and outputs, with 2 8 ohm outs for the 2 passive speakers on the backside I have recently bought a powered sub to add to the system Is there a way to put the sub first in this chain to utilize...

I have a Klipsch powered subwoofer I want to connect it to my TV, which pre-amp would give the subwoofer optimal performance?