Which combination of CPU and GPU should I get for gaming??
1. The i5 3570k and the HD 6870
2. The Phenom II x4 965BE and the HD 7870 GHz edition.
What resolution and games would you be playing?
Depending on your needs the 965 could make more sense especially if its considerably cheaper.
If you can stretch another 25 id get a 7850 vs a 6870.