Help for underseat Subwoofer please

[Timmos1974]

Hi

I have a Toyota Proace 2023 and want to keep the existing head unit, and install an underseat sub woofer that has amp integrated already.

Do i need a line output as the OEM headunit hasnt as far as im aware got RCA outputs...if yes can i just tap into the left hand speaker wires or would i need to trace a wire to the left hand speakers aswell?

Thanks guys