Kudos for reminding about backing up, haven't done that for a while!
I did open the case, vacuumed most of the dust and due to lack of compressed air, best I could do was to blow air through the fans.. I could actually see some dust left inside, so will need the compressed air after all.
I left it powered off for 2 hours, before cleaning the case, and then pulled on the cables like asked, and this time the crackling sound was not there. Wonder if my cleaning helped? Will post an update when I do another cold boot in the morning..
Frankly, I am tired of this Sonata II case now, too cramped, too hot, too much dust.. So I ordered A Fractal Design Arc Midi today, one I kept watching and hoping to buy for weeks!
Let's hope this is not turning into "Found one problem, upgraded everything!" situation
Fractal Design Arc Midi|Antec EA-650|Asus P7P55D Premium|Core i5-750|Gigabyte HD6950 unlocked|X-Fi XtremeMusic|24" Iiyama ProLite B2403WS|Logitech Z-5500|Logitech G11|Logitech G9x