Saw the pictures. But I don't think it has any problems with the 250. The focusing were not spot on. At 300mm, it'll give you a much larger reproduction. Look at our macro section & see the pictures that were taken with 250, notice the difference?
A few months ago I bought a DCR-250 from an ebay store, total cost me about SG$100 shipped here.
I don't really see an issue with using the DCR-250 with the 55-300mm, that guy never explained why he recommended against that, and some other guy posted some nice pics from the 55-300mm + DCR-250