1) GTX460/768M (Asus, Zotac, EVGA have their offer at around USD160).
or spend slightly more for a USD179 HD6850.
These 2 chipsets are much better than the dated 4850 or 5770, in terms of
performance, DX11 supports... as your card will run for the coming years,
a future-proof one is needed for next 2-3 years