Amazed... Welcome ......and is this your real name?
Audio can be a mine field to trouble shoot..........general,intermittent static noise (popping,scratching,crackling) can be attributed to many sources ..........from poor quality speaker cables, electrical interference........lights being switch on or off, close proximity of appliances (routers,modems,desk lamps) which can be moved further away from the PC (4 to 6 feet)
One thing you can definitely try......most will put the troublesome sound cable from the DVD to the board......if you remove this, beside being a posible scorce of your problem......it supplies a poor quality audio signal ....... once removed, your board will reroute this signal as a much better quality Digital signal............and possibly fix the pop
What you describe is most likely poor shielding (Metal case) around your PSU.......Poor quality (shielded) PSUs are notorious for electrical interference when on-board sound is used..........Ferrite clip on filters could be tried but this will be hit and miss......Enacom terminal filters are the bees knees but carry the royal jelly price tag......hope this helps your research.
Aussie Allan