Well, you really have two choices. I think that Kent is a 2nd or 3rd round calibre player, and I would ask for at least one of these pitchers in return for him: Mulder, Zito, Hudson, Millwood, Morris, Wood, Mussina or Prior. I don't think Moyer, Schmidt, Wolf or Vazquez are enough to get back for the 2nd best 2B in the game, and the only really viable powerhouse at that position other than Soriano.
If you can't get at least one of the pitchers that I listed for him, I would keep Kent. Then, try to trade Durham away for a decent mid-tier starter. For Durham, I'd target a guy like Moyer, Pineiro or Nomo. You might also try getting someone like Wade Miller, who has struggled but is turning it around but his numbers are still pretty ugly.