Though I think that it's a good idea to answer the SpeedStep question anyway, I don't think your laptop should be having trouble playing stutter free audio even when the CPU is running at the slower 1.8ghz speed.

I think that instead, you should also be looking for bugs in the audio playback applications, the audio drivers, and the driver/application for that Traktor controller.

Another place to look for stuttering bugs is, surprisingly, the video drivers. I've found that a hitching display driver can mess up audio playback in some cases.