You can use one of these:http://www.crutchfield.com/p_142LOC80/Scosche-LOC80.html
connected from the front speaker outs on the Sony Use a regular stereo RCA cable from it to the ch1 and 2 RCA inputs on the Crown. Set the receiver to stereo or 2 channel since you are not doing surround sound.
The speaker outs on the Crown connect to the amp in on the speaker selector switch. If there is an impedance protection switch on it make sure it is engaged when you use more than 2 pair at once.