Ground Loop Isolators
 

Yes, they have their drawbacks, but sometimes they make a system sound better than without them.
If you are using a GLI in a system (in your RX-8, of course) and have a DC-to-DC power supply or a DC-to-AC inverter also installed, don't put them close to each other. These power supplies generate a lot of noise (which is filtered out of the output line) and that noise will induce into the transformer that is the heart of a GLI. I just spent a couple of hours hunting down a high-pitched noise in my 8's audio system, and that's all it was; I moved the GLI and the noise went away.