Its all about the light.
If any of your cameras have a hot shoe (to mount an external flash) I suggest that and to utilize bounce flash (flash bounced or reflected of a card or wall/ceiling). I also like to use FCB or foam core board (foamboard) which I get at arts and crafts stores. It is varying colors of paper glued to a thin piece of foam which makes it sturdy. Speaking of sturdy, for product shots, or subjects that are not moving - there really is no reason not to use a tripod, or a beanbag, or any sort of steady surface. Save time and do it right in the camera, and you can spend less time fixing it in photoshop, gimp, paint shop pro, or whatever you enjoy using.
The next thing you should look at is a DIY or a purchased lightbox which is similar to a light tent. This could be used instead of a flash or in combination with a flash, and should consist of a box with some sort of frame wrapped in white fabric. Some light boxes come with backdrops, however you can easily make your own with paper and or fabrics. Some lightboxes/light tents come with lights, some do not. You can get away with a few cheap posable table lamps and I suggest using all the same lightbulbs (reduce chances of different temperatures). 3, allows for excellent lighting on all sides (top, side, and front [off to side]) You can make do with less lights, but you have to be creative.
After you get the technique down, and the setup, then you can determine if you need to upgrade your camera or not. If you still want a camera, what is your budget?
