[Ethereum] Mixing two different GPUs on the same mining rig

The 500W minimum you are referring to is for the entire system, including a single card, the motherboard, cpu, fans etc.

The cards themselves probably only max out around 200W each, likely less while mining.

So, you have the 500W minimum including one of the cards, then add the remaining 5 cards @ 200W each for 1000W, and you're looking at 1500W total.

I would recommend going for 2x 1000W PSUs. This gives you some headroom on both so they are not running at full capacity all the time.

The 945W you refer to is the power consumed at any given instant.

Generally speaking, the answer to this question is almost always "Yes."

I've yet to see a situation in which this was not the case. You may have difficulty (but not impossibility) mixing CUDA (Nvidia) and OpenGL (AMD) mining modes, but even Genoil's ethminer is equipped to handle this case.