In my view, you really only have only three options.
Continue to use your D300. Just because better, more up-to-date equipment has been released over the years in no ways makes the D300 obsolete in any way. There are simply better suited cameras available to your existing needs. i.e. Wait for the D7000 upgrade, which will almost certainly not be available before your upcoming trip;
Get a D7000. Great camera, but will probably be replaced soon and then you may be disappointed for not waiting. I have this camera and I have to say that I am still not disappointed with its performance. This will be a good upgrade to the D300 performance wise, but note that you would lose some "ruggedness" of the D300. Low light performance will, however, be noticeably better;
Get the D600. All reports point this to be Nikon's best camera in the price/performance arena. I would upgrade if I had the chance, but that would require not only the camera body, but a bunch of longer lenses too, which is just not going to happen for me in a hurry. Low light performance will be a huge improvement over the D300, but this camera, too, is NOT built to deal with the same level of durability of the D300 (as you stated).
The D800 seems to be an overkill for your stated needs and does not match your frames per second. This is really a specialised camera for studio and/or landscape work and the files sizes are rather large to handle for day-to-day pictures. Rather put your extra available cash to a 24-70 f2.8 for those times when the 70-200 is simply too long for the task at hand........
My choice, given what you have stated as your requirements, would be firstly, the D600, then a wait for the D7000 upgrade, then the D7000. An oh, I would also get a 27-70 f2.8, if I had the funds available.......
While Ken Rockwell does have some interesting things to say, I generally take his views with a large bag of salt. and often seek alternate opinions from his. Many of his views are controversial. I do extensive internet research on may different sites and would recommend that you read the following three reviews:http://photographylife.com/reviews/nikon-d600http://photographylife.com/reviews/nikon-d7000http://photographylife.com/reviews/nikon-d800
Let us know what you finally decide, and ....... no matter the final decision, enjoy your trip