Thanks tomtuttle!

I haven't got the receiver yet, it's still in the mail so I can't tell you what it has on the back, but looking at the online manual it looks like there is a RCA 'sub pre out". I will be using the AVR to manage the base.

The sub has two rotary knobs on the front. The top controls the level of the base relative to the sats (haven't played around with that one in a while). The lower knob controls the crossover from 50-100Hz.

Oh, and thanks for finding the manual!