Additional Information for people looking after OP:
I have a 15″ MacBkPro Mid 2014 with Top Specs (2.8 i7 16GM 1600Mhz DDR3 and 1TB Solid State HD).
I purchased Neat Video Pro 4.2.0
It did not recognize my GPU (GT 750M)
Recommendation was to update NVIDIA CUDA driver, which was very difficult to find:
https://www.nvidia.com/object/mac-driver-archive.html
Installed current driver: Latest Version: CUDA 8.0.46 driver for MAC Release Date: 10/3/2016
(Requires min compute power of 1; the above card is 3, so it is compatible).
Rebooted computer, Neat Video Preferences-Performance-GPU Troubleshooting – Manually selected Enable NVIDIA, closed & restarted FCPx.
Ran Optimizing Performance several times, it never picked the GPU or combo of CPU/GPU.
Best results was CPU only 7 or 8 cores about 27frames per sec (32bits 872x486i).
Moral of the story, use Neat Video for great clean up, don’t bother updating CUDA. Go mow the lawn and get a good night’s sleep while it renders. Cheers, Kev.