I have two emperor 400 and an aquaclear. They both work great but if I were to buy another it would be an aquaclear it is much quieter and works just as well. It is also much easier to do custom media with. That will save alot of money in the long run.
If you have 3 red bellys in a 55 I'd save up and get a canister like a Rena xp3... You can get one used for around 75-100. You have very messy fish I dont think another hob will cut it
especially a penguin 200. i have 1 of those in a 10g right now and i wish it did better. save for a canister. there a lot better and you can set them up however you want. the penguin is 1 way and 1 way only
oddysea also makes this FX5 knockoff, the CFS 500. It makes around 445 gph (not quite 500) and it costs 58 bucks on ebay. I have been using for about 3 months now and I am very content with the performance. It is super quiet and creates a nice current in the 55 gallon tank. with a directional nozzle, you can make it move the surface water, negating the need for a noisy spray bar.
check out my video of me testing it in the sink...