My strategy is to use mesh lights (unseen IDL emitters) rather than a myriad of Poser lights, and then use a modest number of Poser lights right in the area of interest to gain specularity.

     Maybe clever placement of some simple primitives set as not visible in camera and to not cast shadows would give you most of the needed lighting.

     Bob, I render in large dimensions fairly often;  Firefly will use noticeably more memory for larger pixel dimension renders, though it isn't linear, e.g., doubling the pixel area increases RAM usage, but less than twice the previous amount.  The overheating of a video card is a good thought;  even if the fans are running, they may be too weak for the task.

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