My first graphics card maybe a yera back was the gt 545. Now that wasnt very good, but it ran skyrim and bf3 max at reasonable frame rates, your the 640 will do the same.
But you are loads better off getting something in the GTX line of gpus.
Even a 560ti can fit the bill.
Integrated GPUs in APUs aren't necessarily worse than dedicated GPUs, but usually even a low-end gaming card is better than what you'll get from an APU. That being said, you shouldn't be looking at APUs unless you're going for a sub-$400 build tbh.