If you want to baffle the filter, there are a couple of things that you can do.
You can use a sponge-like cover for the intake. This should slow things down a bit. It looks like this (pic taken from a split 5.5 gallon tank):
If that does not work, you can buy sponges for filters at your LPS and cut them to size. Slide it in an open section (preferably behind your original filter sponge thing) of your filter.
If you want a new filter all together, there is a whisper filter for smaller tanks, so I'm sure they make one for larger tanks as well.
This is the whisper in my 3 gallon:
It's a top current filter, so everything gets pushed at the top of the water. No issues as far as swimming, and my fish has fun swimming against the current. When he gets tired, he simply dips under it and goes on his merry way around the rest of the tank.
You can also to put plastic plants infront of the filter (or real ones, but pieces are likely to break off of the real ones) to help baffle it as well. I hope this helps! Out of all of my filters, I have to say that the whisper one is the best one I have.