Running a watercooled i7 with dual GTX 680 which I'd guess comes close enough to a GTX 690.
Haven't tried 4k, but used to run ED at decent framerates on nvidia surround at 6040*1080. Granted, that is 1/3rd less pixels than 4k - but of course that's without SLI. Depending on what FD manage to squeeze out of SLI, I'd guess it should be barely playable with with a few framedrops here and there.
Interesting. I'll probably end up getting a 4k monitor when they come down in price a bit, then upgrading my GPU somewhere down the line. Thanks.