Thanks for all the input guys.
Here's an update: I wandered out to the cable drop to check out the grounding on the cable coax. I found the grounding block... and notice that while they hooked up the coax to the grounding block, and ran the grounding wire through it, they didn't bother to screw down the binding post screw!!!! The grounding wire was barely touching the body of the grounding block. So, I tightened the screw and that killed almost all the hum coming from the coax.
I'll probably try the isolator since I've already ordered it to see if it helps any at all on top of that.
I still have to go deal with the HTPC though, but I think the optical connection will help tame that quite a bit. Those PC switching power supplies and HDD motors are pretty noisy in terms of EMI/RFI. If I have to I may migrate the HTPC to a spare laptop... Running directly off of a DC power source will probably clean up the HTPC a lot.
Mark, I wish you hadn't sent that article! This morning I was calling around to a couple of electricians to get quotes on chemrod grounding posts!
