3DMark
3DMark is the latest version of this hugely-popular synthetic benchmark. Making use of DX11 features such as tessellation, compute shaders and multi-threading, it provides modern-day results and is available as a free download.
A GeForce GTX 780 with a healthy overclock should get close to matching the performance level of a GeForce GTX Titan. The synthetic 3DMark test suggests that EVGA's Superclocked card will do exactly that.