Which is a better way to upgrade WR's

[Bulard280]

I can either pick up a WR, some of the better ones are Davone Bess, Ronald Curry, Bryant Johnson, and Kenny Britt. I think there are some descent producers here however I don't think they really upgrade my WR's that much.

I also have the option to trade Gates/Santana Moss/and possibly Graham for TO/Jonathan Steward/ and Brent Celek. I think this gives me a little more depth at RB and also improves my WR's. I get hurt at TE but I really think Celek is going to have a big year with LJ gone.

Here is my current roster:
QB: Jay Cutler, Matt Schaub, Bret Favre
WR: Brandon Marshall, Santana Moss, Kevin Walter, Donnie Avery, Jermey Maclin, Darius Heyward-Bey, and Juaquin Iglesias
RB: Brian Westbrook, Ladanian Tomlinson, Earnest Graham, and Jamaal Charles
TE: Antonio Gates
K: Bironas
DEF: Giants and Colts