Beckmola, there are many return pumps to choose from. One thing to consider is will this be an internal or external pump. As Cesar has said, heat may be an issue with internal pumps, as is also the case with external (external pumps can get very hot). Mag Drive pumps are great in my opinion. They are also considerably priced. Again they can be used internally or externally, however, i don't advise that you use it externally because it does make noise. It truly is better used internally. Eheim also makes great internal return pumps. They are a bit more expensive that the Mag Drives.
When opting for external pumps, many of those people with larger tanks use Dolphin Ampmasters. However, with a tank your size, I would opt for a nice sized Iwaki pump (American motor or Japanese motor). I do not know the size of tank this is, but an Iwaki 20rlxt or iwaki 30rlt would be great. Remember that it is better to buy a pump that is rated for a higher GPH since you can always lower it. This way, when or if you upgrade tanks, you can still use the same pump.
People utilize closed loops in order to get rid of powerheads (usually the case), or to just add more flow without using powerheads to clutter the tank. So if you have a closed loop, along with a return, it doesn't mean that you cannot have powerheads (or vice versa). Closed loops, like powerheads, are just another way of adding more "flow". However, with closed loops, you will need to drill holes, add bulkheads, and get an external pump to run the closed loop. Some people add powerheads even with closed loops and return.
What size is your tank you will use the return for, and what will/are you keeping in this tank?
- Elmo