"One question I do have though with the EP4000 is:
If I am running 4ohms per channel, gains all the way up, this gives me my max output up to 1400W/ch yes? So if I set the gain knobs to halfway, is that effectively attenuating the output signal so I get only a max output of 700W/ch?
Forgive me if this is a stupid question."
it is a good question.
first of all, the ep4000 won't put out 1400 watts per channel into 4 ohms for more than a millisecond. real world output is more like half that.
second, on pro amps, the gain knob doesn't indicate % power. the way it works is your pre amp send a voltage to the pro amp input. the pro amp then multiplies that by some factor and outputs that to the subs. the "input sensitivity" is the minimum voltage that is required to hit max power with the gains all the way up. however, if the input signal is very strong, the amp may still hit max power even with the gain knob set half way up. it is a little tricky and why pro amps have clip lights. most folks simply monitor the clip lights and adjust the gains up or down without trying to figure out input voltage/multipliers/ or any of the rest of it. consumer amps don't have clip lights because consumers would be upset if they knew how frequently their amps were clipping!