I've heard Eheim is a good brand. I used one for a while and went back to a HOB filter (Aquaclear 50) because I was afraid my kids would figure out how to unhook the hoses, plus needed floor space, plus HOBs are easier to clean. I'm sure if you get used to them either kind would work fine.
If you get a canister, go for one that has an easy priming feature, because having to mess with getting the water in the hoses or suction by other means is a pain.
A better upgrade IMO would be to go for 2 AC110s - 2x 500gph plus larger media capacity (I think) vs. the emperors.