The vs450w will be fine, a gtx960 can only have a maximum draw of 150w with a single pcie 6pin connector, that leaves @300w for the rest of the system. You'll have anywhere from @75w to @150w worth of headroom depending on your cpu.
Just understand this though, the VS series is bottom of the barrel when it comes to Corsair's psu's, so please try not to push the wattage to extremes.