Only a 50% increase? Are you sure that, as a result of not noticing the extra resources due to the far more powerful machine, you haven't thrown in more complex content, higher rez's, more lights, etc, that would slow it down? When I went from an 800mhz PIII to my 1.4 Athlon render times of IDENTICAL scenes were nearly half. When I went from that to my current dually, it was even better....