This is the wrong adapter if you want to connect your Sony with the stock infinity amp.
Instead of chinch outs you'll need normal wires, because the speaker outs of the radio will be connected to the infinity amp.
There are only 2 channels needed for the infinity amp.

You will need something like that, but without the plugs on the left side.
Or you can use it by cutting of the plugs on the left side and connect the wires to the plug that came with the Sony radio.