It is dependent on how much you want to spend.
The GPU is one of the few things I would keep from your rig.
Buy a new CPU, Motherboard and RAM. If you currently don't have the money for all that, start buying things separately (1.RAM 2. MOBO 3. CPU) (you might as well sale your old parts to save money).
Upgrade that SSD to something from Samsung, you will see an incredible difference in speeds.