I don't think you'll currently have much luck with Display Port currently, unfortunately. Display Port support is something both Cyfm and I would like to get addressed, so it's not something that's completely forgotten about at least, just something that hasn't yet gotten done.

If by 2k you mean 1440p (rather than, you know, 1920x1080, which would be 2k the same way that 3840x2160 is called 4k), then as Asiegel points out, dual link DVI should be sufficient for that. Now whether or not the mentioned hardware actually supports dual link DVI I don't know, but I'd expect at least the 4650 to do so, and I'm also not entirely sure whether MorphOS will correctly use dual link DVI hardware on those cards.