The x2 555 can be unlocked to a quad core if their stable and u have a motherboard to unlock them.
If u cant get the cpu to unlock, a new cpu as a fx6300 has the best performance for its cost, a A10 5800k would do way better than that A6, but if u have a dedicated gpu than an amd apu is pointless.
A new gpu even tho the 5830 is not terrible, new architecture, less power draw, and basically wat u usually would get buying something new its just up to date