Also take into account that rendering engines are starting to licence by the core - 8 cores = potentially 8 licences.

http://www.3delight.com/en/index.php?page=3DSP_pricing Offers a superb professional rendering engine, free for mono/duel cores, but to get the full power you need to spend. As multi cores have improved and OS's become more stable with them plus the potential for even more cores, virtual or actual, then there is the potential to run on multi processor motherboards, you just know more and more rendering engines will start to take this kind of licencing approach.

Martin