JEEBUS! Heres a question though apart from the price why was the GTX580 bought more than the 590? Is it simply not as good as it could/should have been even with dual GPU's?
Also with the 590 you got the microstutter/tearing issues apparent in SLI cards as that is essentially what it is IIRC!
With 28nm parts in short supply i can see these things been very rare. Think its a shame they haven't put out so more mid range parts. Maybe another round of price cuts to 560/570GTXs?
I've read somewhere, that the GTX 680 is nVidia's top single GPU card for this generation and that the elusive GK110 is either the code name for their dual GPU offering (most likely and apparently supported by some of the latest comments here) or the code name for a specialised version of Kepler geard toward HPC (think Tesla). GK104, as it stands, isn't really usable in HPC scenarios since nVidia scaled back GPGPU performance in favour of raw gaming performance.