200w PSU is obviously outdated and it also depends on which company are u using. Get a 600w coolermaster PSU 80plus certified. It should run your games awesomely. ALso, see to it that u have atleast 8GB ddr3 1600mhz ram. You're gx270 has a 2.2 Pci-e x16 connector so it should work just fine.
If u find any problems, feel free to PM me.
Take care