I know that Eheim pumps are the popular favorite, but I tend to like powerheads like the one in this thread and Maxi-Jets due to their small size. Yea, I know that Rios are powerheads, but look at these quick powerhead reviews/descriptions:
http://saltaquarium.about.com/cs/prpowerheads/
Powerheads seem to be ideal for a small case due to their small size.