Sorry for the delay in replying.
Others have covered it well, I think. Having looked at your examples, to be honest, I do think you'll see more improvement in your results by focussing on technique, both shooting and post-processing, than you'll see by buying a new body. If you have some available cash, then the suggestions made of a flash (like the 430ex), a good tripod (Gitzo/Bogen/Manfrotto), or an IS lens (17-55/2.8 IS comes to mind) should be considered priorities.
In particular, you should concentrate on the following (in my humble opinion): exposure parameter selection for subject (shutter speed adequate to freeze camera/subject movement; aperture giving best DOF for subject - use the DoF preview function to check; ISO as low as possible), scene composition (no distracting background objects; no trees growing from people's heads, etc), and lighting (natural light direction; where do the shadows fall; flash usage for fill-in or primary light; bounced and diffused). Shoot RAW (or RAW+jpg) to maximise your flexibility (e.g. changing white balance and 'exposure' after the event). In post production, experiment with cropping to aid composition, and get a firm grasp on using the unsharp mask tool. One useful technique is to convert your image to Lab mode and sharpen only the luminance (L) channel, then change back to RGB. USM sharpening parameters should start at around 250% amount, 0.5 pixel radius, and a threshold of 0 to 2 (higher for noisier images).
