I've got way to many running backs.
You can never have enough RBs.
I wouldn't make the trade because your WR depth is thin compared to your RB depth. What would this guy give for Benson by himself? Could you offer Benson and either Orton or Hill for an upgrade at QB? Don't go overboard trying to trade for a QB if you don't get a favorable offer, though. Orton/Hill have potential and you will have all season to upgrade the position. You should constantly be on the lookout for the QB currently on your waiver wire who will finish in the top 10.
That assumes that you only have to start 1 QB, because every QB should already be picked up if you start 2. I can't believe there have been 18 responses without anyone asking about your scoring rules and starting requirements. In order to be able to give the best advice, I would really need to know if its PPR? How many RBs, WRs, and QBs you start? And if its a redraft, keeper, or Dynasty league? These criteria make a big difference in fantasy decisions.