I have the latest BIOS (1.2.3) and audio driver update (7989) and am having this problem. Not sure why. I can end the Service Application and the CPU consumption stops, but this makes it such that the Waves MaxxAudio software can't detect a headphone being plugged in.
The huge CPU consumption only occurs when I'm using the internal speakers. No problem with CPU consumption if the headphone jack is used normally.
EDIT: I found one way to trigger the problem. USB audio is causing the problem. I can reinstall all the DELL audio drivers and it would work well until I plug in the first USB audio device. Then it starts messing up whenever I use the internal speakers regardless of whether or not I have a USB audio device plugged in. My headphones can't be detected at all after this.