D.Rowe, I am using a Marantz SR-96.
At the time I bought it it was their top of the line receiver.
I know currently there are very few receivers that have main in's but it use to be more common.

As for your volume dilema I would probably set the 950 to 0db and start the test tones, then raise the volume on your pioneer until you are about the 75 db spec on an SPL meter.
Set your individual speaker volumes on the 950 from there.

Definatly take a pencil and mark the pioneer's volume in case it get moved by accident.

Got my tracking number today so now I'm just waiting to rip my whole system apart