Ok so after reading the whole thread again.. It would appear to me the issue is NOT with your headsets or soundcard or USB soundcard, the problem lies with your motherboard chipset bus or cpu, is your bios upto date? Do you have access to a second system to test your soundcards and headsets?
EDIT: My reason for saying this is due to you having explored all avenues including:
Sound card, software and drivers.
Windows media settings.
External USB sound card.
Onboard Audio including front panel header.
3 different headsets including ear buds.
Fresh OS install.
And yet your issue persists, something on your motherboard is borked and giving you, forgive the pun "Crossed lines", the problem "could" it's a long shot, but that your on board audio chip set is conflicting with any sound card, be that PCI or USB. Try disabling all but the one you intend to use, if the problem persists after that then you are more than likely looking at a motherboard that is on its way out sadly.
I'm not an audiophile and haven't had a dedicated sound card since 1997 which back then was the Sound Blaster AWE64 Gold but back then you actually needed one, once manufacturers started putting audio onto motherboards I stopped looking at dedicated cards for just gaming and a playing music, I saw them as a waste of time and money as they are really for like editing and studio stuff and there is nothing wrong with on board, but that's just me.