Newbie Preamp Question

What Level to set Preamp at?

I'm still new at all of this so excuse me if this question has an obvious answer. I purchased a new preamp (Anthem TLP-1). The preamp has a function to independently adjust the input of all sources from -20 to +10. This is supposed to make the sources come on at similar volume levels. For example, if you switch from CD to Tuner, the volume of going from one to the other should be similar if I understand it correctly. By adjusting the input level of the preamp, you can change the level of the sources. Hopefully this is making sense. Right now I have the inputs set at "0" or flat. Everything sounds fine to me but I'm wondering should I have it there or maybe at -20 or even +10. If I have it set at +10, I don't have to turn the volume up very much to really increase the volume to a higher level. Consequently if the preamp is set at -20, you really have to turn the volume up quite a bit to get loud volume. I'm wondering if either of these settings is harder or less hard on my equipment? Does anybody have any opinions on where I should keep these settings? Thanks for your suggestions.
I think what your talking about are gain settings for each impute, whichever setting lets you have control over volume adjustments that you like is fine. I have a tube pre-amp and the hi-gain setting is more dynamic but noisier ( requires quieter tubes) not a problem for you enjoy.
I'd suggest you set the volume (s) on each item so the background noise is at a minimum or a non issue altogether.

So adjust the amp up where you can run up and down the vol with the preamp + source, so there aren't any artifacts, hiss, him, etc. as the vol goes up & down when normally using your gear... then leave it there and forget about it.
If you are happy with the gain matching from each of your sources, that is they are not so disportionate when changing from one to another that its irratating, just leave them flat. Do nothing - they are only there for convenience.

FWIW, if I had to use them at all for matching purposes, I would choose to lower the settings of the majority to the level of the quietest source than the opposite, which I think is sort of the result of doing what Jim has suggested. I'm very sceptical about using any amplifying source between the source output and the line amplifying stage in the pre-amp.
Thanks for taking the time to respond to my post. I will take your advice and run with it. :)