It's called bottlenecking, meaning one part (CPU) is too slow to keep up with another part (GPU), so the graphics card has to wait for the CPU to send it the data that needs to be rendered (drawn) on screen. Thus a powerful GPU paired with a mediocre CPU means the GPU will end up being data starved, and not reach it's full potential.
Plus the Titans are overrated for gaming. They're really more raw compute power GPUs for workstation applications that require LOTS of VRAM and intense calculations. Gaming GPUs are more for quick graphics rendering draw calls. The type of graphics used in games that benefit from high FPS.
The 900 series are more geared toward pure gaming and actually benefit more driver wise for it. The TechPowerUp chart for the 980 show it outclassing the Titan in performance. In fact a Titan 6GB is even about 5% less performance than the $300 970 in games.
http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_980/26.html
Never buy a GPU on VRAM alone, or price for that matter. You have to take all factors into account, esp real world gaming benches.
If you've had the Titan too long to get a refund, try targeting sites that have graphics pros that need a card more like a Titan if you want to sell it. You'll probably get more resale value that way.
If you manage to sell the Titan without too much loss and insist on lots of VRAM for high res, consider the 980 Ti. There will soon be both reference and aftermarket versions of it, with a variety of price points. You only list 55" TV for display, so it would help if you'd mention whether it's 1080p or 4K res. You definitely don't need the 6GB VRAM on the 980 Ti for 1080p though.
That said, if you have or are planning to go to a 4K display, the 8GB VRAM cards coming out may be better suited, though we won't really know until the AMD 300 series officially launches and gets thoroughly tested. Note that the 8GB versions will be special variants, the default amount is 4GB. Though with HBM (High Bandwidth Memory), the memory bus can easily handle it.