Thank you for supplying empirical evidence, DustRider.  I'll tuck that away.  In my case, my cards wouldn't help much, and I wouldn't see that as being worth the potential instability of Lux GPU-only or GPU hybrid mode, but I will reconsider the nVidia cards' useability with Lux.

    Heddheld, no shame in external mounting, my friend - creative adaptation that works is a good thing!

     Ghonma, I absolutely concede that rendering in Octane on a Titan (or two, or three) would be faster, and even adding the cost of the Octane license, would be cheaper.  But that only applies if you are rendering in Octane.  I primarily render in Poser's Firefly, or in Vue, and have only begun to use Reality/Lux.  There are also other processing uses for which I can use the blades, but not GPU.  Titans will not avail me in Firefly or Vue, and Lux is shaky at GPU rendering, and loses accuracy and geometry/texture capacity.  I tend toward big complex scenes, so that is a considerable drawback to Lux GPU-only mode.  Octane wouldn't suffer that geometry/texture limitation;  that's why I said that if I ever build a GPU render rig, I would get nVidia cards and an Octane license.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5