I got a PC600 set up yesterday and have been having trouble with the sub, in the sense that it doesn't work at all. I went to Best Buy today and swapped it out for another, and still I'm getting nothing.
Thought it might be the auto on/off switch, so I jacked the sub volume level up in my receiver settings to near maximum, and still not even a peep from the test tone. I've also tried reversing the phase, and a new Monster cable.
Exact same setup works fine with the sub from an old $300 Sony HTIB. Using a Yamaha RX-V1800.