if you are planning on getting two cards down front, get 5750's, if you are going to wait, then 5770s
for reference, the 5770 is equivalent to the 4890, in terms of clocks and compute power they are a direct comparison
in terms of an upgrade from a core 216, I would probably get a 460 1GB as the 5770 is very similar in performance to the 260 and the 5830 is worthless at its price, but I have no evidence of the 460 1GB beating or losing to xfire 57xx.....not yet anyway
