Yes it is enough for either of them
750 Ti consumes only 65W at peak load and doesn't requires any 6 pin PCIe connector.
260x with peak power consumption of 120W requires single 6 pin PCIe connector and your PSU can power either of them without breaking a sweat.
Also your PSU can deliver 34A on +12V rail.
Your system with 260x will require about 25A on +12V rail while when paired with 750 Ti , the system will consume about 20A on +12V rail. So you have plenty of headroom with that PSU