I have both the K2 and the DX and use them both. The K2 is perfect for bedtime reading and traveling and holds all my fiction. The DX is used for magazines & non-fiction and stays at home.
The larger screen on the DX is good for Readers Digest and sitting in a chair reading. It is a little heavy for reading while lying in bed. It took a bit to get used to the page turn buttons only being on one side but I hardly notice now. I use both readers about the same amount nowadays.
C.P.T.