yeah 5770, 6850(if you want a higher spec but with a lower budget) 6870
I have both a 5770 and a 6870 Black Edition form XFX. Really great gaming from both these cards.
FYI - the 5770 is known for being a bang-for-buck card
so you can;t go wrong with it. Remember
, the 6770 is not a next-gen 6xxx series card, its just a rebadged 5770 with a slight higher OC. Otherwise it has the same engine under that cooler shroud.
Hope this helps