1. 5750=4850 (4850 is slightly faster, but is older, more energy hungry, and runs hotter--its also $30 cheaper)
2. 4770 (not a good deal at $110 when you can get the 4850 for $99)
3 5670 (fastest reference card you can get without a power connector--but much slower than the above choices)
If u on a plan to buy, then tell us the rest of your system and how much do u want to spend...
I would prefer 5750 from options above.
But we need more info here, just like dragon said...