i kind of regretted upgrading my body to a d300 before investing in better lenses, but got over that pretty quick once i realized that light has more effect on image quality rather than my body/glass
... and here for you in this case, you reached the point where the camera was more important than additional glass. This is the same that happened to me going from D200 to D700, but not before I had accumulated some excellent lenses. There comes a point where the best glass in the world cannot give you the results you need becuase the camera is the main limiting factor.
I was very often frustrated when taking photos in dark places, or any other low light scenario. Even when I was using strobes, I often had to crank them to 3/4 or full power and still not get quite the results that I wanted. With the D700, not only do ALL my lights work at a consistently lower power level (saving me batteries and increasing the life of the components), but I am getting the results that I want and more.
Now, for 95% of the people, camera before lens is not going to work for them... why? Because they are at a lower knowledge level and are not exploiting their current camera AND lens, much less a more expensive camera. However, once the knowledge does start getting into the head, normally the first thing that does become the limiting factor to getting good images *is* the lens because most people start off with kit lenses which are the lowest quality and most limiting all around. Of course it will be easy to make big increase in image quality over low quality and/or kit lenses.
Once lenses are no longer a limiting factor, or like in my case, *any* lens will not give the desired results, that is the time to move up to a better body. During this process, one accumulates good quality glass that will serve you now and in the future.
"They" say that when it comes to photography, there are 2 areas where you buy the best and buy only once... your lenses and your lighting. Cameras and other accessories are replaced and upgraded every few years.