Honestly, you probably don't need it. If you want to keep that extra focal length then by all means go ahead though. If you need cash for another lens though, the 55-250 should sell for near $200. It's always a thought. Fact of the matter is though your f4 lens should be waaaaaaaaaaaaaaay sharper and have better color; another bonus is that since you're on a crop sensor your technical focal length is 88-320. Granted you lose 80mm if you abandon the 55-250, but again... do you really need it?
You wouldn't happen to have a RAW version of this would you? I'd like to take a crack at a B&W conversion if you don't mind.