My replacement surface 2 came in today. Even after all updates, the sound is perfect across the board. Even Netflix, youtube and other web videos sound good.
I had the speaker problem where everything sounded bad, even the system sound test. Left speaker was 30% of the right speaker. Right speaker still not very loud. Both speakers distorted, tinny, and sounded blown. It started right after an update that first weekend after release. Bluetooth and ear buds sounded amazing. It was only the built-in speakers that were bad.
So if your audio symptoms are like mine, go to the surface support website or fall back on your retailer's warranty plan or what have you. That's what I did and going to Microsoft support via the online chat was not a terrible experience. For a bad situation, I'd even go so far as saying the service was excellent. It took them 4 business days to get me a replacement under the Advanced replacement program (you guarantee you'll send the broken surface back to MS after you get your replacement -- with your credit card).
But even while my internal speakers were terrible, everything else was excellent. I still had my surface with me everywhere I went and it still became an invaluable part of my life. So, sometimes you get a lemon (and I'm notorious for getting the lemons!), but MS made it right with as little pain as possible.
Soo, what you are saying is playing songs from the xbox music raido and mp3s, with the audio enhancements on, you do not hear any crackling or distortion at all when the volume is maxed (both the music app and windows volume control)
I'm listening to some heavy dubstep right now and no crackling or distortion -- xbox radio