I'd agree with Paul, that the coulters typically aren't necessary. 

Further reading here (Exapta's Tech Tips for Planters), here (Mojo Wire), and here (Thompson wheel).  Those with fast connections (or plenty of patience), might be interested in the article by Lyle Carter on the Library page -- ideal no-till planting involves firming the seed at the bottom of the furrow, and placing loose material over the seed.  Dwayne Beck has made similar statements on many occasions during the last 15 yrs or so.