That card with your psu will probably give you a blue screen of death in the middle of a game.
If upgrading the power supply isn't an option then I think this is a complete list of all your options.
Radeon HD8570
Radeon R5 220
Radeon HD4550
Radeon HD4350
Radeon HD3450
GeForce 9600 GT 600Mhz
GeForce 9400 GT
GeForce 8400 GS
GeForce 8300 GS
GeForce GTX 730 GDDR5
GeForce GTX 730 DDR3 128bits
GeForce GTX 730 DDR3 64bits
GeForce GTX 720
GeForce GT 620
GeForce GT 610
GeForce 605
GeForce GT 520
GeForce 510
GeForce GT 420
GeForce 405
GeForce GT 320
GeForce 315
GeForce 310
GeForce GT 220
GeForce 210
GeForce 205
GeForce 100
If it was me I'd put them all in a spread sheet.
Look up the rank for each one here
PassMark Software - Video Card (GPU) Benchmark Charts - Video Card Model List
Then look up the price for each one at ebay.
And pick the cheapest one with a high rank.
---------- Post added at 09:00 PM ---------- Previous post was at 08:53 PM ----------
A minimum 350 watt PSU is recommended for AMD R7 240.
All the cards I listed recommend 300 watt min.
There isn't anything for less than 300 watts.
The AMD R7 240 might run but you are going to be cutting it real close. If you can try it for free, I would. But I wouldn't buy it because the odds aren't great.