Without knowing about the flow issue, I got my first two filters from walmart of all places...They're cheap, being about $10.00, and they're the waterfall type, but they've been great filters.
So, they're not adjustable at all, but they can be baffled SOOO easily with some aquarium sponging. Just cut it to fit the outflow, stuff it in there (top of the sponge in the outflow, bottom of the sponge hanging out into the tank and *into the water*), and close the lid. The lid holds the sponge in place, and cuts the outflow/current down to 0. Seirously, there is NO water movement once you've sponged it. (This tip is from someone else on this forum, I'm wanted to give credit, but I'm not sure who it was, but it was a fabulous idea whoever came up with it!)
And the sponging doesn't hurt the filter at all. I've had two going for a year now, and two others for the last few months, no ill-effects to the motor or anything else. I think it's because the sponge doesn't stop the outflow, it just absorbs it and allows it to soak into the water instead of letting it fall. So the filter flow isn't being affected, just how it the water exits the filter.
Plus I love the additional surface area for cycling. :)
Oh, and this 5-15 gallon sized filter with the additional sponging for the outflow and the intake can easily accomodate a good cycle on a 20 gallon divided with two fish and a billion or so snails. (The snails were an accident...) ;)