On the back of my all-in-one stereo system there is only one port for aux stereo rca input and I was wondering if there is a way to put two devices going into them.
This is a very bad thing to do. Two outputs will be trying to drive each other. This is definitely not the best setup, you could possibly damage one or both of the sources.
Spend $20 and get a switcher, it will be worth it...