If you find it is not a sub-amp problem, you might consider looking at a power center, (Pure AV, Monster etc.)which will give you the option of delay on/off switching which will be easier on the circuit. Maybe a stupid question, but is the cable going from your AVR to the sub ok? Considering the limitations of positioning of the subs, I don't know whether this would be an option for you, but in my case with eight pieces of equipment including two multi-channel power amps on a regular 20 amp circuit, without the power center, I probably would be blowing fuses every time I turned everything on.
