Head unit voltage out

Hey everyone,
I'm just brainstorming here, I was wondering if anyone knows what the rms voltage out from the stock head unit to the amp is? I'm thinking of maybe retaining the stock amp and speakers for awhile, and just installing my DVD head unit and sub. The stock speakers sound great and the amp seems to be good enough for the time being until I have time to install my a/d/s components. I've got all these great ideas but no time to complete them. I know it's a tough question.