I use my pair of EP400s using the 'Speaker Input Terminals' as my Tube Integrated Amp has no other outputs.

I can assure you that the 'Speaker Inputs' utilize the subs' internal 500W amps. There is no way that my 35W/Ch Tube Amp will drive them to high levels by itself. Besides the Gain Control on the back of the subs increase/decrease the output of the sub amps & hence the overall volume. Furthermore, the On/Off Switch kills all sub sound output when turned off...

TAM