I'd definitely look at grounding first. But since this came up after moving the wires around, it may be this: Do you have any wires inside the case that carry audio? Like and extension wire that gives audio to jacks on the front of the case or something like that? The reason I'm asking is because in car audio it's a big no-no to bundle power wires with audio wires. You're guaranteed noise that way. I've run power wire down the passenger's side, audio down the driver's side, and pc stuff (usb, led's, switches) down the center. I have ZERO noise. And I haven't grounded my case separately (yet). Point is, if you bundled some 12v with some audio, you'll likely increase your unwanted noise. Try to separate those if you can. If they must cross each other, do it at 90°, like a "+". Also, ground the case. Between both of those, you should be good to go. Hope this helps.