There has been quite a bit of discussion on which PSU to purchase at the KNC forum. The bigger 1000+ Watts PSU will not only offer better efficiency at around 50% load, but the lighter load (relative to max load) will also be easier on the PSU, extending its life and reliability. The extra wattage headroom might also be useful in case the KNC chip turns out to be highly-overclockable. On the same PSU KNC forum thread, one of the KNC staff has already l leaked Jupiter will run at an expected speed of 500 GH/s!
True and maybe some people can just wait for more info but there is a point of diminishing returns. Lets say the Jupiter is 500 MH/s. >850W @ 12VDC would mean >944W @ 120VAC. That is >1.8 J/GH. Already close to double what bitfury does @ 55nm and more than double all other 28nm offerings. I certainly hope it doesn't require even MORE power than that, I am hoping it will be significantly less power even when overclocked. Then again it isn't like more capacity hurts I was just pointing out the "much lower efficiency" at high load is pretty much a misnomer at this point.