between the three mentioned (HD 4770, 9800GT, GTS 250), the best would probably be GTS250. kasi ang GTS250 is kung baga improved version of 9800GT. meron lang konteng improvement na ginawa sa GTS250 (as one review said, the GTS250 is everything that 9800GTx+ should have been). pero clock for clock, mas mabilis konte ang GTS250 (by around 3 or so frames).
the drawback of HD 4770 is ts only 128bit, although DDR5 siya, the 128bit factor is still something that would pull it down (kaya siguro nasa price range lang siya ng GTS250 kahit DDR5 siya). the better ATI version would probably be HD4890 (mga around 7K siguro).
btw, the one you will probably get now is the green version. this will NOT require a 6-pin connection to power supply. mas matipid kasi ito sa kuryente so kayang kaya ito ng HEC 500W