Pre amp voltage is only an issue if you are looking to do one of the following; drive multiple amplifiers, improve signal to noise ratio, or are using amplifier that require a high voltage input.

Most good amplifiers on the market today require about 250Mv input to reach their rated power. Some companies have even chosen to make their amplifiers more sensitive (at the risk of higher noise levels and as a way of making them louder on display boards when compared to better sounding amplifiers) to the point where you only need 100Mv or less.

So, you might be thinking why is it that companies promote more than what is needed. It is a simple approach really.

In adding an amplifier you will adjust the gains at the amp, in most cases that means applying gain at the end of the signal chain, which in-turn automatically means you are amplifying the original signal+noise. Relatively speaking that would mean the amount of noise at the speaker will be louder.

By making the signal at the source higher, then you wind up applying less gain at the amp and as such the noise level is less.

Other factors related to amplifier performance and how to compare CEA 2006 rated amplifiers is attached.