New GFX Card for a Dell Vostro 430

Hi



I need something to replace the Graphics card in my other half's Dell Vostro 430.



Everything else in the PC seems OK, but currently its the suffering very low FPS in newer games.



Currently its a 1GB NVIDIA GeForce GT220.



Other key specs are:

4096MB (2x2048) 1333MHz DDR3 Single Channel

Intel Core™ i5 -750 (2.66GHz, 8MB)



I realise the PSU might need to be replaced, but it does have one PCIExpress 6 pin power adapter.



What can you suggest? Looking to boost performance without spending to much money.



Thanks