jheiminga's comments you can take to the bank.
Good lenses will outlast several editions of bodies. A Rebel XT with good glass will produce far better images than a 20D with low end lenses on it.
An example can be found in
www.dpreview.net , go to the 350D forum and search on Daniella, she is a birder and is very good but she also uses some of Canon's good lenses on her Rebel XT.
The number of pixels is not as important as the size of sensor they are squeezed into and the camera's internal software that processes the image.