In your position, I would go RB-RB. I don't think the top WRs are as clear-cut this year. IMO, there is about 11 top guys (SS, Chad, Harrison, Holt, Wayne, TO, Fitz, ROY, R.Moss, Evans, and Boldin). After that, I think there's a little bit of a drop off into the Walker, Housh, Burress, AJ range. Since there's so many differing opinions on the top 2 WRs, you really have no idea how this will turn out. Wayne or Roy could be #1 by season's end, so it's not necessary to take someone like Harrison or Holt so early.
My drop off of top tier WR's ends after Roy from your list, I have some major question about the guys after that which prevents me from putting them in my top tier. I`ve projected that the 3rd round is when the major run on WR's will start and since I`ll be picking at the bottom of that round I`m a bit concerned about what WR's will be there, and if WR's are flying off the board in the 3rd that should mean RB's are falling. The RB's depth is so solid this year because guys like Bush/Marion Barber who people would never touch years past because of RRBC, are solid #2 and #3 backs.