The way your team is built, you could take two separate tracks. I guess first off is Justin Faul would be the definite "D" man to pick up and add. Given the fact that all that young talent is still available, I am making an assumption that the owners in this league do not value up and coming talent over the established players unless they are the sure fire studs. From the list you gave I personally would look at either Callahan or Koivu if you are looking for the established no question types. If you're looking for the longer term answer I'd choose either Kreider, Nyquist or possibly Ennis who started to turn it around at the end of last year.

__________________
Head to Head 12 team 14 man keeper League F:Ovechkin, Marleau , E.Staal, Getzlaf, Gaborik, Krejci, VanReimsdyk, Benn, P. Bergeron, Little, Hodgson, Turris, Burmistrov, Michalek, Read
D:M.Green, Keith, Letang, Byfuglien, Ekman-Larsson, Spurgeon, J. Moore
G:Lundqvist,Lehtonen, Pavelec, Halak