How Many Desktop PCs Can One Server Replace?

NZheretic asks: "HP has just announced that they have upgraded a four-processor server with Advanced Micro Devices' new dual-core Opteron. The amount of processing power a multi-processor multi-core system can deliver seem like a waste of processing power for most traditional servers, which are more likely to suffer from disk access bottlenecks before lack of processing power becomes a problem. But what if that power could be delivered direct to the desktop users? The HP ProLiant DL585 supports eight 64-bit PCI-X I/O Slots (Six 100MHz, two 133MHz). The ATI FireMV(TM) 2400 supports Quad DVI/VGA displays on PCI Express. Assuming that you leave one PCI-X slot for a multiport USB card, thats up to twenty eight displays with USB keyboards,mice and headsets that could theoretically replace twenty eight networked desktop PCs. Using DVI and USB extenders, not all of the user stations would have to be within the 7.5 meter cable distance imposed by the DVI cable limit. The only OS currently capable of supporting this many displays is Linux. What limits would be imposed by the hardware and PCI-X bottlenecks? Taking into account the added cost of the HP and ATI hardware, could it deliver a great reduction in the total cost of ownership over both traditional PCs and thin client systems? How many desktops is it practical for a high end server to directly replace?"