I have the Rift DK2 and also 3 monitors.
The E : D view in the rift is awesome, literally, and I'm pleased I've been witness to it, but I routinely play on my 3 monitors.
I wouldn't get too excited about CV vs DK2. DK2 renders each eye at 960 x 1080, CV will probably be 1280x1440 (DK2 has a 1920x1080 screen, I'm guessing the CV will be 2560x1440). I don't think that's enough of a change to make much of an improvement (try playing E : D at 1280 x 1440 and max that up to a 50" screen and see what you think.) The CV should improve the pixel layout and reduce the 'screen door' effect though.
Re performance, the GPU has to render the scene twice, once for each eye. You need to maintain a framerate of 75fps (DK2) and possibly 90fps for CV. Plus the DK2 render target for the GPU is actually 2364x1461 (to compensate for the distortion that will be applied down to 1920x1080). Equivalent for the CV would be 3152 x 1770. Plus stereo rendering is still in its infancy with the Nvidia / AMD drivers so it is not the most efficient. So you should expect to need a 970 / 290X minimum for the CV, and turn things down to low. If the CV resolution is actually *higher* (there's a chance it'll be 4k) then all bets are off - the main issue if Oculus does this will be that the GPU demand will be enormous - I think even a single 980 would struggle.