You’ve got dual GPUs, and dual cores, so why not dual transformers?  The Tagan EasyCon XL 700W that SPCR reviews has just that, to go with the quad 12V rails.  Each can handle up to 20A (56A total) and 672W are devoted to those 12V lines.  There were a few issues discovered along the lines, so keep reading before you run out and buy one.
“We’ve been anxious to get our hands on a Tagan for some time now, as our forum members have often commented that they have the potential to challenge for the silent crown. We got one at last, and it’s a high end doozy: 700W, modular cables, dual transformers… what more could we want? Well, there’s always low noise… Can we count on Tagan’s reputation?”

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