Please do note: The likely final spec for Oculus Rift is 1440p, with 90Hz refresh rates. This is the assumed spec of the unreleased (yet critic previewed) Crescent Bay build (beta 3) of the Oculus Rift.
1440p eliminates the "Screen Door" effect caused by lower resolution displays, and 90Hz appears to be the necessary refresh rate for high speed in-game movement (either of your head, or of elements you are watching fly past you at high speed). Refresh rate is actually extremely important, as slower speeds can cause 'tearing' effects on high-speed action.
I do not know whether the GTX 750 Ti can handle these presumed final specs for the consumer Rift.