Should I upgrade my GPU?

[PenMonk]

OS :Windows 7
MOBO: BIOSTAR H77MU3

Processor Intel(R) Core(TM) i5-3450 CPU @ 3.10GHz, 3101 Mhz, 4 Core(s), 4 Logical
Installed Physical Memory (RAM) 8.00 GB
GPU: GeForce GT440

I was thinking of getting a GTX660 :
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I want to be able to run ArmA 3 better (and just run games in general). Should I upgrade the GPU or will it bottleneck somewhere else?

Thanks,
Josh

P.S. Right now I only have the fans that came with my case( one on the side and back). Should I add another one for a new GPU?

 

[Wisecracker]

Make.
That.
Move.



edit
(depending upon your PSU!)