I see no reason to attempt a highly complex render all at once, especially in P6. I mean, if you have 15 characters in a scene, for instance, you can always render out in layers, and now with the new shadowcatcher, and the ability to render a seperate shadow pass, rendering objects/figures seperately to ease render burden is more than a viable option. Compositing the scene in post also gives you more control over the final result. Unless you absolutely refuse to do postwork (for whatever reason), I don't see a problem with that kind of workaround.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.