Go for better lenses first. Even with digital cameras the lens is still the premier source of image quality. If the lens isn't top drawer it doesn't matter how expensive the camera is - technology can't put back sharpness and contrast that wasn't there to begin with.
If you think you may eventually upgrade to full frame or any 1D series camera then I agree that lenses such as the 24- or 28-70L are a good bet. If you intend to stay with APS format then the 17-55mm f2.8 IS is worth looking at too.