[Moved to Hardware forum.]
Unless your getting into media with resolutions greater than 1080 then there wont be a significant difference in performance right now. This also depends on the CPU and ram available to feed the GPU.
Thanks guys. Particularly, I notice when using a denoise plugin, or adding effects, my real time playback gets pretty slow and sometimes unwatchable. I don't transcode videos, typically I use them right out of the camera (DSLR or GoPro, mostly). I figured more CUDA cores would help alleviate this problem.
Rest of my config:
Intel Core i7 3770k OC to 4.2GHz (cooled with Coolermaster Hyper212)
Asrock z77 Extreme 4 mobo
Corsair Vengeance RAM, 32GB
Corsair HX750 PSU
Case is a Fractal Design R4
Scratch Disk - 120GB SSD Kingston SSDNow (Sata 2)
OS / Apps: 240GB Samsung 830 SSD (Sata 3)
Media Storage: RAID1 1.5TB Seagate 7200rpm drives
That sounds like the CPU is close to max processing capability. Convert the Go Pro to Cineform and see how it runs then.