For wiring question:

From the stock deck there are 8 wires coming out to 4 speakers

- Front right (+) and (-)
- Front left (+) and (-)
- Rear right (+) and (-)
- Rear left (+) and (-)

How many line-level converter do I need?? Do I have to combine them first?? Basically how do you wire these outputs to line-level converter and then to the amp??