I remember you said that insufficient power can sometimes cause similar symptoms. I've looked at my Beat Audio control panel and in the advanced settings under "Power" it was set to go to a power saving state after ten seconds. Could this have been causing the popping noise? I've disabled it just now. It still pops once when unplugging a headset, but I'm not sure if the laptop does that regardless and I just haven't noticed until now. We'll see if the random popping continues.
EDIT: Also, no word on what could be causing latency spikes, though again DPC Latency Checker isn't detecting any major fluctuations.