static/electrical interference sounds from speaker

it's just process of elimination. You'll be unplugging interconnects, powercords, and speaker cables to see what's the offending cause. Once you find it, you can issolate it.
Are your speaker cables touching anything with power? Are they in the wall or on the floor (possibly touching some other gear?
Otherwise, yes, try disconnecting sources, one at a time (including interconnnects), and see if the noise goes away.
(also, there is no reason you can't use the cheater-plugs on some of your pieces, as long at you have at least one or two of your components in your system grounded safetly - as they'll all be connected anyway, and thus grounded.

If I'm wrong on the "grounded anyway" thing, someone who's an electrical expert PLEASE ADVISE othewise!
No-one wants to get electricuted here, I'm sure.

Funny, while I'm looking at this post, I noticed my little computer speakers were making the same noises - lots of crackling and static sounding. I moved some wires off the speaker wires and power cord, and the noises are all gone. It's the same kinda stuff. You'll have to move things and trouble-shoot