at 3 cores, it will severely bottleneck..
But at 4 cores and 3.5Ghz, it's much better condition than original.
remember, athlon class lack of L3 cache, it's a fps penalty if you compare it with phenom II class with L3 cache..
So, you still have a slightly bottleneck on your system..
But don't worry, most games right now is more GPU bound rather than processor bound..
So, your processor still have a chance as your gaming processor..