hello, i've just read your topic... and i wanted to see it by myself.
So here we go.
While using the "top" command in x-term, i started listening to music :
- with the speakers, pulse process went around 22% and 30% of the cpu use
- with headphones, cpu utilisation drops between 7% and 12%. I tested with Senheiser HD650 =P

So what do you think ??