So, IRAY defaults to CPU on large scenes. I have a 64Gb system than often runs at over 25% RAM usage while rendering, so I'm guessing that most of my scenes would be over the 3.5Gb usable memory in a GTX970 (although that doesn't take into account memory savings from instancing)... so is IRAY any faster than Luxrender running on CPU?

BTW, getting back to a previous comment... aren't .duf files proprietary DAZ file structures? Isn't .jpeg a common platform standard? How can you compare accessing the two as the same thing? I know DSON is an interface to allow some access to .duf files for Poser users, just questioning the analogy.

I also just downloaded DS4.8 to check it out on my AMD card... less than 5 minutes before I closed it; a new record!

Memory needed by the render engine is different from that needed for the scene. DSON is a content notation format, like a cr2 or an obj file or even a jpeg file, though a jpeg file is binary and the other three are text files. No, DSON is not proprietary. 

The DSON Importer for Poser is a plug-in for Poser that allows for the import of the DSON format. It uses Poser's Python interface.