Hi Jonathan,
It is not a dumb question, but a very broad, or vague one. The answer is very specific to other factors on your system and material.
A simple rule that I always go by is to push my signal as hot as I can so I can maximize my signal to noise ratio. That being said, I also leave tons of room for dynamic changes in the material.
There is no absolute answer to your question. But here are some thoughts:
If your signal level is low on the input of the console, and your system output is too loud, than you have a gain structure problem in your system. Same goes for vice-verse. First you would have to address your gain structure problem, than worry about your individual signal level. (In a perfect world)
On the iLive systems, I’ve been having pretty good results with my levels averaging just above the fake 0VU on the channel meters. I find myself mixing a little hot on these consoles. I haven’t heard any complaints yet. 
If I’m doing an event on an unknown PA system, I usually will have my main outs feeding a Stereo Matrix and output that to the PA. That way, I can have my Main busses at a good level for board mix or distribution and adjust my PA on the matrix output. Which will, therefore, help on my signal to noise ration once again.
Sorry for the long answer. Hope it helps some.
take care
Gil
Gil Parente
Design & Integration
Entertainment Arts, Inc.
