Which part to upgrade

[Cranial]

I have a decent desktop with the specs:

CPU: AMD FX-8320 (Non-OCed)
Mobo: Gigabyte 990FXA-UD3
RAM: Corsair 8GB (1600 MHz)
GFX Card: EVGA 650 Ti Boost 1GB
HDD: WD 7200 RPM 500GB
PSU: Cooler Master 600 W

I am looking to spend around $150-200 this boxing day to upgrade.
I have been thinking about getting a SSD.
Apart from the SSD, what would be a good choice to upgrade this PC's specs, within 150-200$.

I basically just play WoW/Dota2. They run well enough, but I want better performance

Thanks for any feedback.

[Deleted]

An SSD is a nice addition, no direct performance increase to FPS but still worth it.

Overclock your CPU if possible, you can get a fairly cheap aftermarket heatsink like a Cooler Master 212 EVO or Enermax ETS-T40-TB. Make sure there is enough room in the case, they are quite tall.

As for a GPU I'd look at a GTX 760 or AMD 280:

Asus Radeon R9 280 3GB DirectCU II $160 after rebate
Gigabyte GeForce GTX 760 2GB WINDFORCE $170 after rebate