I bought a house that is pre wired for speakers 7.1 set up. Bought a used receiver ( only tx-sr706) which has power for all my speakers. Turns out my subwoofer is passive and this receiver cannot handle the additional load of the sub. When I search amplifiers online they seem to be car focused. Can somebody recommend a decent and affordable option and what wire(s) I need to buy to connect amp to receiver? I don't have any specs on sub as it is in the wall and I inherited it. Thank you in advance