Anecdotal evidence, but I had a desktop PC and later a Mac Mini pretty close to a 650W 12" sub and I'd have the computer on and that sub rocking the world lots of times and never had a problem.
You are right, it would seem that something like that wouldn't be good, but I think for components, things fit really tight, so vibrations wouldn't really do anything there. My concern has always been mechanical hard drives, but like I said, I've never had a prob.