I think the D5000 could be a tad bit bright for him. Moreover the leak some sound, but not as much as Grados or Senns. IMO HD600/650 should be about perfect, being the HD25 the natural closed alternative for him.
For a different flavor, but still musical, nuanced and quite right, what about ESW9 or ESW10? You'd not even need an amp.
Oopps just noticed that jinp had suggested those already