I think Calzaghe goes first if he beats Hopkins, but until then only Hatton has beaten guys recently at different weights, and went 8 rounds with a guy who beat up a 7 footer
If Haye can make some damage in the Heavyweights, I would put him up to 2.
Khan for me hasn't proved anything yet in terms of P4P - not his fault, just the way these things progress. I think once he comes up against some decent opposition we can see how good he really is.
Overall I don't think anyone can be considered in any P4P discussion until they have at least 25 fights - you then should have a decent title and had a few tough fights.