Ground Distribution Block Substitute

Would it be safe to take the ground lead from a point in the chassis, run it to a capacitor, then connect the ground leads of 2 amps directly to that capacitor, rather than running a distribution block?

Thanks in advanced.

Here's the situation. I currently have a 4-channel amp powering my speakers, totalling about 500rms. I would like to add another amp (300rms) to power a sub I just got. As of now, this is running off 4awg wire (is this sufficient for both amps?). I know I need a distribution block for power, but I wasn't sure if I needed one for ground as well (wanted to use ground terminal of cap as distro...) I'm safe running a 100amp fuse in the main line, right? Should I just bump it up to a 150amp fuse?

By the way, the cap is only rated at 0.5 farads... after coming here, I realize it was probably a waste to get in the first place, but now I'm stuck with it.

1. No.  You don't have to have a ground distro.  Ground each amp to chassis near each others ground point.  2. 4 ga. is enough, and keep it fused at 125 amps or lower.  3. You're never stuck with something someone else might want.  Find somebody with Audiobahn stuff....they'll take ANYthing.

and 4.  No relay is needed for just two amps.  Just run a wire from amp 1 over to amp 2...or what you said.