Can my psu support a gtx 750 ti 2gb?

Just disable the haswell c-states (C6/​C7 Low-Power States) in the BIOS of the motherboard, so the haswell sleep states shouldn´t be that of a problem.
Could be that your system would randomly shut down, when the processor enters those states, so by disabling this in bios, it will be fine.

Which motherboard are you using?
 

Im using the ASROCK B85M-DGS
 

Thanks!