Been married 30 years, in that time I think I have upgraded cameras 5 times. Each time I have passed the old one to my wife and got the new one for me. She has been happy because I had used it enough to be able to teach her all the tricks and she never cared about getting a new camera. But she is a one in a million or maybe 10 million.....
If it were me I would get the k-5 and pass the k-r on. But I'm not sure I would try that until after you are married.
May not work for everyone but what I have ALWAYS done is ask: Honey, I am going to get a new camera, would you like my old one or do you want me to get you a new one as well. At least that way you know and she shared in the decision. And trust me, that is really important if you want it to last. (The marriage I mean. The camera is on you