Did you get the Elysium in the end twilyth? I'm planning to get one for my SR-2. Simply the best value for money case for the 2P boards.
*looks at the wooden board underneath the cruncher* - "you're not a case, that doesn't count"
With regards to the motherboard sizes E-ATX & SSI EEB are both 12" x 13" with holes in same place. From what I've seen, doesn't look like there's any changes to layout with the newer spec you mentioned, but not sure enough to recommend you anything. Perhaps get in touch with Asus customer support?
Dual 8-pin CPU ATX power supplies are easy to find, like the Corsair HX/AX 850 and above but no idea if the SSI standard is compatible. I remember seeing on another forum that AMD Arima boards needed to have those connectors forced the opposite way.
Guess I'm just as clueless as you here, but either way free TTT in the hope some server guru sees your call to arms for help.