[airspirit]

Modifying a R300 is done by desoldering and moving a resistor on the GPU packaging. Very detailed but definitely doable. There are many tutorials online.

I would go with the opterons. The prescotts are a bridge platform that will only exist until Q3-Q4 next year when Tejas comes out with yet another socket. You will be unable to do any service to those PCs in under two years time, you will probably still not have the performance benefits (and possible 64-bit support if it appears) of the opterons, and they put out over 100W of heat on the LOWEST MODELS. Did I mention that they will probably be more expensive than the opterons?

I would NOT look at a prescott platform. You'd be better off with a current P4 than that ....

As for the watercooling or Prometia: opterons don't need supercooling, so that's out, and unless you are going to build watercooling systems that are either externally contained (such as the EXOS or some such), easily maintained by IDIOTS, or both, I wouldn't go that route. There would be too much liability if something goes wrong. It is an office environment: tell them to deal with the damn fans ... not that you will have that much of an issue on them since they don't run horribly hot.

Also to add to the mix: duallies do very nice in rendering, especially in CAD programs designed to take advantage of it. That right there is enough to put you on the opteron path, I would hope. Keep your eyes peeled, however, since you may be able to use Athlon FX chips in the place of Opterons and get more bang for your buck ... though this is yet to be determined.