Far Cry 2
The Dunia Engine was built specifically for Far Cry 2 by the award-winning Ubisoft Montreal development team. It delivers the most realistic destructible environments, amazing special effects such as dynamic fire propagation and storm effects, real-time night-and-day cycle, dynamic music system, non-scripted enemy A.I. and so much more.
Unlike the HD 5750, the HD 5670 does struggle to break 30 FPS at 1680 x 1050 at the Very High presets. The good news is that you've got a fair bit of wiggle room when it comes to detail with the ability to drop to medium which should yield the extra numbers you need.