does anyone know what the stock speakers RMS is in the 07 G6?
both the 6.5" and 6x9", and what does the stock head unit output?

Most stock head units put out like 14w per channel. It all depends on the sound system if it is amplified or not. RMS on stock speakers is fairly low, but also depending on which system you got. Why may I ask?

I can't give you the exact number but I would say your 6.5" are prob 25-45RMS? and 6x9's are prob near 60-80RMS? I am not really sure. Every car I had I always gut the sound and put aftermarket in. :)

I like this guy^^^ But I would say lower, you are better off using a loce and running all new wires.