Is it possible / advisable to modify a PE plate amp's rumble filter? I have the model without bass boost, and I want to keep it that way. But as my next sub will be tuned to 20 Hz, I'd kinda like to move the rumble filter up to 20, and perhaps make it 4th order. Too much cone excursion below tuning. Long, long ago I think I read something that stated you could borrow an op-amp from the plate amp's XO to increase the order of the rumble filter. I can't find any of this info anymore, though. Can anyone give me any information about this? Alternatively, I could just buy the Rythmik plate amp that has a setting for a 20 Hz highpass, but it's probably only second-order, right? Any advice? Thanks!