That would be interesting.. also what about the GTX 680 and 780? How do those compare? What card would give you the most bang for your buck currently? Titan Black would be the best performer? But how usable are the 680 and 780?
And what is the current minimum about of GFX ram that is advisable? 3GB, 4GB, 6GB? Assuming we are getting 4K and 5K material from time to time (and more in the future probably).
3GB will be enough currently for 4K but 6GB is definitely where you want to be if that is an option. Keep in mind GPU acceleration is constantly evolving which means caching models change and use far more ram. The coming GPU accelerated debayering for Red will further increase ram space used on the GPU's. However keep in mind system ram is used to create the buffers and shadow to GPU ram. So that means you need to increase the system ram to utilize the greater GPU ram.