The JBL GTOs are pretty efficient at 92dB and the P80.4 can get them plenty loud without even working hard. I feel like I'm blasting it at halfway and I really can't even listen to it over three-quarters because it's too loud. Still not distorting, either, at that volume. The P80.4 has quite low THD and the rating of 40W seems very conservative to me.

 

You can think of pre-amp voltage kind of like a radio signal - the stronger the signal, the clearer the reception.

A strong pre-amp voltage means less noise, and less work for your amp. For example, let's say your gains are at 1/2 on the amp, with a 2v input signal. With a 4v input signal, the volume through the speakers will be louder with the amp gains still on 1/2(not sure it'll be twice as loud, but you get the idea). So higher input voltages mean your gains on the amp can be at a lower setting while still maintaning good volume.

BTW - the MP7019 has 1.8 volt pre-outs. Here's an info page for ya': MP7019 @ Crutchfield

~HH