I run a few FX5s and so far I've been very pleased.
You figure those statistics are measured without media, so the flow isn't going to be as high as you think. I've found the best method with these filters is to just put the ceramic rings in the center chamber and just use the filter pads on the outside compartments.
I was running activated carbon in the center when I first got them and my tank looked like shibby because the filters were constantly shooting out really tiny bubles and it looked like a bb cloud...I was not happy. I just dumped the carbon and switched to rings and prefilters and I've been a happy man ever since.