I want to trade away Vernon Davis. What is equal WR value right now?

Moss would be roughly in that range - he's slightly outscoring Davis right now. Gaffney, who you already have is about the same range as Davis. Ask for Royal, you might be able to get him because the Broncos spread the ball around so much, but I really wouldn't expect to get the current #13 fantasy WR (standard Yahoo scoring) for a TE on a struggling team even with Davis' rep.