The 7000 series from AMD are the current gen cards. They will last you awhile. the rumors are the 8000 series will be out in February, so about 4 months away IF
the rumors are true.
The 7770 is a good card and does OC very well like greghome
Here's the comparison benchmarks of the two head to head
Visual comparison of overall performance...VERY
close. For the price, get the GTX 460 unless you really want to drop more coin on a better card.