Sorry to bring up the same question again, but I need some clarification.

I just installed stereo system in my girlfriend's 2001 Civic and I got the same problem.
I put in Pioneer head unit, Rockford Fosgate speakers and some cheap amp off ebay. I didn't have time to get a decent amp yet so I had to hook everything up to this Sound Storm 200W RMS amplifier. I rand the RCA cables on the drivers side together, power cable on the passanger side. Amp is in a trunk.
When car is in accessory, everything sounds great, when engine is started the buzzing starts, it's low pitched, it doesn't hurt your ears, music blocks off the noise but it's still there. It also increases in frequency with acceleration.
Could that be still the grounding problem (even thought it starts when car is on)? Or should I pick up a better amp faster?

Thanks