Hey guys. I created an account for this board just to tell you this one thing: the issue of crackling and popping sounds during playback or recording is directly related to the USB controllers on your mainboard. Yesterday I installed an internal PCI-E USB card, plugged my Scarlett 18i20 into it and what do you know? No crackling, no popping, no latency issue, nothing. Just pure audio.
I strongly advise you guys to get one of those cards, too. I paid no more than 15 bucks for it and it was a extremely useful investment.