I suggest to save until you can afford both items for the upgrade. You won't be happy with either a CPU or GPU upgrade alone. Trust me, I had the A6 5400k before.
If you don't want to wait you could upgrade to a A8 6600k and use the integrated graphics for the time being. It costs around $80.
Also the A6's integrated graphics should be more powerful than the 5450, so I would go ahead and remove the 5450 and see if your games become more playable. Also make sure to use DDU to cleanly uninstall any left over drivers before installing the drivers for the A6.