The part of that "Voltage Gain" article that concerns you appears to propose a highly unlikely combination of an amplifier with below average input sensitivity and a pre-amplifier with a low maximum output capability. I looked at the Parasound's specs and saw that it had the THX standard 28.28 volts output for 1 volt input(i.e., 100 watts into 8 ohms)and a 1.6 volt input for full output.

Any receiver of the quality that you're considering(I'd also think that the X4000 looks best of those named)should certainly output enough voltage to fully drive an amplifier with a recognized standard sensitivity. No X4000 test results appear to be available, but when Audioholics tested the fairly similar Denon 4310, the max pre-amp output they measured was 4 volts.

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Enjoy the music, not the equipment.