my engineer friend mentioned two things he fixed/replaced ...
a resistor and some technical term I didn't remember.

yes, I have compared the 500 to the DLS-5000R but just for the DTS demo U-571. the 500 is less boomy but also has less kick in the chest. the 500 has more pant flapping powers though. also, my ceiling joists now rattle when the ep500 is at the 8 oclock setting.