Re: Superfast 6-Screen Compiz-Setup.
Looks like he is using two matrox triplehead 2 go and twinview instead of xinerama. At least, thats how I would do it ;-) I don't think there is a way to have anything done fast with xinerama.
This way you don't need that much hardware resources.
I have a dual screen setup using twinview with an elderly geforce 8800GS and downclocked it to a third of the stock speeds, without noticable changes in 3D desktop effects speed. This would not have worked before 195.xx though, the speed of 3D effects were notably slower with the older drivers.
BTW, the guy in the video uses kde and not compiz.