If you can still play all the games you want with it, there's no need for an upgrade. By the time you can't, more powerful cards will be out, or the current existing line of cards will be cheaper.
You'd get buy with nearly every game on just a 5870 and you essentially have two!
Mobo: Asus P8Z68-V-PRO | Processor: Intel Core i7 2600K @ 4.6ghz | CPU Cooler: Zalman CNPS9900MAXR | Videocard: ASUS GTX970 Strix
Memory: Patriot/Kingston 16GB 1866mhz | OS SSD: SanDisk Extreme 240GB SATA | PSU: PC Power & Cooling Silencer 750W
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