After doing a lot of research on cat nutrition, I have decided to feed a mostly wet diet, with dry out to nibble on during the day.
Since going on that diet, Sammy has lost weight (which he needed to - he was a dry food junkie, and it showed in his body mass) and has much more energy.
Here's an article that I found interesting, written by a veterinarian on nutrition:
http://www.catinfo.org/