Dell Optiplex 780 SFF Graphics Card & Power Supply Help

Hi, I want to upgrade the graphics card on my Dell Optiplex 780 SFF with something decent for  gaming, such as NBA 2k15 and have it run smoothly on medium settings, but the only cards I am able to find require atleast a 300w power supply or larger. I've been looking around for a power supply to upgrade to, but can't seem to find anything bigger than my current power supply which is 235w. Do I still have any options left, or is it time for a new pc?

SPECS
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Dell OptiPlex 780 SFF
Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz
Chipset: Intel Eaglelake Q45
Physical Memory: 8062 MB DDR3 SDRAM
GPU: nVIDIA GeForce 210
235w Power Supply