I'd love to buy one of the new 4k monitors, but I'm not sure my machine supports it. I have the latest model (2013) 13" Macbook Air. Apple's website lists the following supported resolutions: 1440 by 900 (native), 1280 by 800, 1152 by 720, and 1024 by 640 pixels at 16:10 aspect ratio; 1024 by 768 and 800 by 600 pixels at 4:3 aspect ratio. But I've heard rumors that the 2012 Macbook Air did work with the 4k resolution 3840 x 2160, even though it wasn't listed as a supported resolution. Supposing my model of macbook air doesn't work with a 4k monitor, can I use some sort of external graphics card to drive it?
The resolutions you have cited are native resolutions for the internal display. 4K apparently works, though, and the HD5000 in the 2013 Airs is more than capable.