If you would like to use your 1980's pre in your system you can. You will only need to insert it between your pre-pro and your front channel amp. L+R pre-out from prepro (or receiver) will connect to aux or another input on your two channel pre-amp. For hometheater use, you would need to set the volume control on the two channel pre to the equivalent of pass through mode (unity gain), this is usually 12:00 O'clock. This is the position you will need to return the volume control to each time you watch a movie as this is the point you will have set over-all volume balance from in the pre-pro setup of all channels. Of course all two channel source will only connect to your two channel pre-amp.
Dave
Dave