in my cubase 6.5 when i playing with some plugin and vst instrument there is no problem, cpu 30 to 40%, but when i scrolling the song window up and down there is some sparking noise in speaker.
Start by raising your soundcard´s buffer size.
What sound card do you use? Are you using USB mouse, or BT?
You could also try moving the speaker(s) farther away from the (screen) monitor
HTH hope this helps