Hey rudybeet, I have faced a similar issue with a Pro Audio sub I had some time ago. At low volumes on my AVR the sub wont wake up until I crianked the volume (on AVR) up a bit. Turning volume up on the sub all the way didint help. I ended up increasing the sub level in my AVR byt 3dB and that helped. Have you tried doing this. If you are selecting crossover through your amp, turn it up all the way on your sub.
M60s, QS8s, VP150 and paradigm Ultracube-12
Samsung BDP-3600, Nintendo Wii