I Own C/L/R 3000
Hey,
You should connect either the mid or high terminals via speaker wire to you AVR. For the built in sub-woofer you have two good options:
1) Leave the jumpers connected to the low level terminal, and it will take a tiny portion of the signal from the connected speaker wire to drive the subwoofer.
2) Connect the RCA connector to the CENTER channel pre-out of your AVR, and remove the gold jumpers from the low level binding posts.
It is important to NOT use the LFE output of your AVR (use the center pre-out), the subwoofer in the 3000 is not designed to be used as an actual subwoofer, just to extend the frequecny response of the center channel.
Nathan