well based on the memory overclock, being a little bit higher than the stock one is capable of (they say 1250 but most people can get 1350 out of the reference board) i'd say they are pretty set on elipda modules, and from the anandtech overview, they seem to believe that there have been no modifications to the board itself other than maybe a binning process.
i totally agree that 4k is the future, but is still not consumer available enough (still $800 for the cheapest consumer model) to worry about with the current generation of cards. perhaps by the next amd release we will see 4k being more popular, and that is when you may see 4k become really popular, but other than that I don't expect 4k to take off until maybe next year sometime (when 120hz 4k tech comes out it will make 60hz 4k much more easily affordable).
Sidenote: you do need to try and find more than just one reviewer, as the silicon lottery does favor some over others (linus has a shit 290x, but a king of a 780, TTL had a shitty 290x as well, but a pretty good 780. It seems like the only reviewers i can find that actually DID get a good 290 or 290x were anandtech and (H)ardocp, while virtually all others tended to have poor overclocking samples of the 290 and 290x. Were i a reviewer myself, and had access to both cards. Icurrently own an asus 780 that i fully admit to being the holy grail of the 780 chips @1256 on the core and a +486 mem offset ((yes, samsung modules ftw)), but when doing comparison numbers from other review sites, none of the 290x's even come close (ok well they come close, but 72 in unigine valley vs 70.2 or so on the highest 290x i could find) for the price difference found in north america right now. At base prices, the 290x wins, absolutely hands down for what you get vs what you pay; but the nvidia price drop, combined with the amd price hike, has made the amd side a MUCH less favourable option in north america.
With the performance gain in single card setups with the 780, i may not win at 3x 1440p, but at a single 4k it's neck and neck; and I'm fine with that because i make enough money to live comfortable, but am not about to spend over $2000 on a personal computer, and then another +$1000 on monitors, because that simply isnt sensible to me. when a 4k monitor is under $500 for a decent one, the hardware can run modern games at the level today's hardware can run today's modern games, then this will be an option. Considering my single 780 i5 rig scores within the 90th percentile of computers in 3dmark, i would expect the masses would be relatively in the same or worse boat than I am.
(quick edit) the 3dmark benchmark was run over the christmas break with 3570k@ 4.8ghz for time of the statement's sake