Basically, the SL-2 and D-75 together are a stand-alone system, that source components would be plugged into. Just as with your Sony receiver.
There is really no good way to use both with the Sony. It would require pre-amp outputs – not all do – to connect to the D-75 amplifier. There is no good reason to connect a pre-amp like the SL-2 to a receiver.
Regards,
Wayne A. Pflughaupt