Great info and tests. One comment however is that, with such low average render times on most machines, particularly the Opteron, the overhead of simple file I/O, frame switching, etc. may be skewing the results. In other words if rendering a frame takes an average of 3 seconds, and the combination of file I/O, frame switching, etc. adds an overhead of even 1 second (which is more than likely), a full 1/4 of your "render time" is composed of non-render operations! The nice thing about this is that, while render time scales with frame resolution and scene complexity, overhead will tend to remain roughly the same (probably increasing slightly with complex scenes). So basically what you want is to increase the ratio of render time to overhead so that overhead comprises a much smaller percentage of your total render time, and thus you get a more meaningful idea of how much extra machines will really help performance. I suggest individual frame render times of 30 seconds to 1 minute on your median machine for best results. The results may not turn out significantly different, but it's worth the try. - Oshyan