By reading the specs of this machine, i think the Z800 has overtaken Mac Pro as the most powerful personal workstation...
check out the latest Nvidia FX cards, wonder if they beat the ATI 4870 out of the water?! beside the cable-free system in Mac Pro...everything else is beyond what MacPro can offer...well, maybe it's too early to tell but from the spec of the Z800, it looks indeed to push MacPro out of the way