Personally I dislike .co unless it goes with a single word in such a way that it makes one very short brand name. Because the best thing .co has going for it is that it's short. Once it's paired with 2 words and 4 syllables, it loses its appeal for me.
And .co just doesn't rank in search results.
I wouldn't hope for much from this particular domain. If it were the .com, I would aim for $1000 to $2000. As a .co, however, I wouldn't bother.