Make it three of us, although my post is coming in a bit late. The amounf of control you get when wiring your ground vs. an unknown path on a case can make a difference.
In the car audio world (in the 90s), I built a probe which had a little Radio Shack amp+speaker in the middle of the circuit. With the car running, and the little amp on in one hand and the connected probe in the other, one could search for a quiet ground spot on the chassis. For instance, if you wanted your amps in the trunk (like a normal car audio nut) you could usually find that that easy-to-use bolt had far more noise than some weird spot six inches away. Sand away some paint, drill a hole, and an excellent quiet star ground location was yours.
Geez, to think I used to go through similar hassles...and had to mess with the weather as well. Head-Fi is so much better!
