Satellites yes, sub no.
I think the manual says 11" minimum. I have mine under my desk and the monitor on the desk (suprise). No problems, probably 12 inches or so from the top of the sub to the base of the monitor (21" viewsonic).
Just leave the monitor on when you are installing the sub and watch for any discolorations/wavy lines. If you see them it's too close. Don't leave it there for long if that stuff starts happening, can damage monitors.
Also keep it away from your computer (hard drives).