I also use salt water sumps on my freshwater tanks.
I disagree about the trickle filter though. I use the trickle filter configuration of my sumps and find it very beneficial! The trickle filter provides a huge air / water interface which is great for oxygenating the water as well as off gassing organic compounds. I even go so far as to put an airstone under the trickle filter to maintain a constant supply of fresh air up through the bio-balls as the water falls down through the bio-balls.
If you choose not to use a trickle filter you should still be fine. The open design of a sump is much better at oxygenating the water than pretty much any other type of filter.