From a video quality standpoint, you are comparing the right two products, Oppo and K, regardless of their price. By all accounts, both are essentially the same in video quality. You get what is on the source.
User interface, of course, is drastically different. For me, its not worth the price just to get the awesome K interface, since I can get the video quality I need by connecting hard drives to the Oppo and navigating the archaic interface. If it didn't mean sacrificing some other part of my theater for the funds to buy the K, though, then I would certainly go for it.