We’re getting the minimum specs for a VR-ready CPU rather than for graphics cards. Rift’s recommended specifications ask for a Core i5-4590, with no mention of the AMD equivalent. A10-7890K chip from AMD can’t compete in terms of sheer horsepower to some of Intel’s Core processors. Because AMD’s CPU catalog doesn’t quite reach the performance parity with Intel’s chips.      Link

Also, performance at a particular resolution isn't solely reliant on running the lastest and greates hardware at max details since 1) most people aren't that passionate to spend their rent on a computer (it is just a game, playing it doesnt require a financial minimum) and 2) high resolution displays (as such buried in Rift) have been around for over a decade and the hardware powering them at the time is comparable to modern cheap hardware.
 
IMO, at this point minimums are just marketing for the hardware companies. The progress of any technology trend depends on what the majority use it for, not the minority passionate enough to get the best hardware to run Rift.  I think most will realize that Rift is just a miniaturized dual display and only the type of game they play will determine whether they need the minimums or not.  It isn't any different with any resolution.

With VR being super new I think the first Gen stuff will need all highend flagship gear to run smoothly.