The 7770 is high end.
Yeah I would agree, people would always say the GTX 550TI was low end but I could run bf3 ultra settings on any map, Skyrim every single setting maxed out (even 8gb AA), Assassins creed 3, Far cry 3 on max settings (20-30fps but its playable and didnt seem lagg). The AMD 7770 is better than the GTX 550ti so imagine what else you could run.
@OP you could probably build a new computer if you want with that amount of money, Windows will probably bump it up a bit by $99 if you get OEM version.