Wait at least until the reviews come in on the new screen they're using for the graphite DX. That same screen will almost certainly be on the K3, and if it really is 50% better contrast, it will be worth the wait for the new model. Contrast is one of the biggest complaints about using an e-ink reader.
Since the new DX ships this week, you'll see people posting here and on kindleboards quickly enough that you should still be able to pick up a cheap K2 if you decide to. Or wait for the new model to come out, there will be plenty of people selling their old ones to upgrade...probably complete with a plethora of accessories that won't fit the new model.
Some will even have extended warranties...my Square Trade warranty still has nearly two years to run, and is fully transferable.