So, with 5 or 6 people on g+ hangouts, I seem to be using up 2-3 processors on the amd x6. I also have a standard Nvidia card, and am using the nouveau drivers. I'd love to get up to 10 people and see if the extra heatsink fan starts blasting. I can do that on a video conversion to mp4.
I've tried running Yade (discreet elements), and can get a reasonably big simulation, but the fan only seems to bump up a little.
So, if you want a good hangout experience, then you've got to go all the way with the big hardware for fully open Linux (no binary drivers).