ground amp

I am a car audio novice. I have replaced my head unit, in-door speakers, added an amp and 1 10" sub. It's a Pioneer head unit, Dual XPR2500 Amp, and the subis Rockford (I know, crappy equipment). The amp is bridge. My problem is that I can't seem to find a good spot to ground the amp, or at...

So, i currently have one amp that is grounded at this point with 8awg wire.. And im going to be wiring my second amp in a couple of days, but im wondering, if its ok to use the same ground as that one ^. like just put the new ring terminal and wire on this ground aswell? However, on the...