So if it makes you guys feel any better, I will tell you my story. On my 55 Gallon, I switched from 4 HOB filters to a SunSun 304B. I wasn't blown away at first by the flow, especially since the 304 is made for a tank bigger than 55G's. Now after having it few a little while, I realize the flow is pretty good, becasuse a HOB is moving water at the surface, while the spray bar is about 5 inches under water. If a fish swims into the spray bar, it will get pushed away.
When I was setting mine up, it seems like it would have been easy to put way too many 90 degree angle bends on the return going to the spray bar. Try and make sure you have just the one.
How is the water level in the tank? That will affect the filter. Also, is your spray bar in the water? Or is it at the water level?