hate to double post, but worthwhile to add - i have two identical machines, except one has the geforce 670 and one has a radeon 6780.
the geforce 670 one i'm not presently using, so if there are any strange issues that need examination, i can just walk away from the machine, contact you guys, and when/if you reply then i can fire gdb off, or whatnot.
also means i can change operating system versions, kexts,or totally mess the machine up if required... all in the name of science
can give you guys remote access aswell (ssh, vnc)... xcode and gdb are already installed.