I have the crackle as well, and also have trouble with my in-ear headphones no longer working with the device. The 3.5 mm input doesn't recognize them anymore. My home cans work, but I'm not one of those doofus' that walks around wearing cans in public. It's disappointing, I am now going to have to either go through the hassle of trying to exchange an EOL (T-Mobile) device and possibly be stuck with the same problem or buy an iPod shuffle for music and be done with it. I'm overall very satisfied with the phone but you're right, a phone that touts its audio specs shouldn't have basic issues with playing audio.
Update: just got a replacement 8X from T-Mo after having the 3.5 mm plug stop recognizing earphones. That problem is fixed on the new one (for now) but the crackle is still there as well. Must be across the board on all 8X's. So annoying.