My build at the moment includes: ASUS Crosshair V-Formula Z with an AMD FX-8350, 16 GB of G-Skill RAM, an EVGA GTX 670, and Corsair AX850 watt power supply. My question is whether it would be prudent to upgrade my CPU to the FX-9590, or my graphics card to the GTX 780, or something else all together. I enjoy playing various games including FPS's, RTS's, etc. Tell me if i need to include any more information, I am not quite sure whet else you would need to know. Anyway!
Until that system cannot do what you want or need, I wouldn't upgrade. In the past I had that "need" to always have the best...damn is that expensive. Very easy to spend big money on small gains. Then 6 months later the next "step" get released. In my opinion, it is way more satisfying to me to upgrade every 2 years and get an awesome jump in performance.
780 is more effective, if you want to buy a 9590 i would probably then suggest to buy a liquid cooling kit instead for half the price and OC the hell out of the 8350.