Stan, Like I said, you want to have a continuous ground from your new AC sockets > to your sub panel > to your main panel. If you put in a new ground rod 70' or more away from the one at the main panel, there could be a potential (voltage difference) between the two ground locations causing a current in the neutral leg -- you don't want that.
How does the 8AWG transition to the 10AWG -- through 4 breakers at the sub panel? I hope so! And do you have a 40A breaker (or fuse) at the main panel where the 8AWG takes off?
I think what people mean when they tell you to star ground your panel is slightly incorrect. I think what they really mean is to star wire it. That means that each duplex outlet in the wall should be wired directly back to the panel with a hot, neutral and ground wire, and not daisy-chained with other outlets like is done in cheap plug strips.
But electrical systems MUST BE GROUNDED (for fire insurance reasons if nothing else!) When you finally plug everything in, you will probably want to lift the ground pin on all the three prong plugs of all components except the one on the preamp, UNLESS -- you are A.) using all balanced interconnects, B.) a Balanced Power unit, or both.
If you have breakers at your sub panel (and I hope you do!) you can wire a little high speed diode between the equipment side of each breaker and ground. If there's a power surge or lightening strike, the diode will close, grounding and thus opening the breaker, before the surge can hurt your equipment (of course you'll have to replace the diode!) but it's a way of getting great protection without any sonic degradation -- which you do get from most power units that incorporate traditional surge protection circuits (the ones that can be reset :~)
