It would be used to render complicated game scenes(low polycount, lots of texture maps) or high poly game concepts.
I was thinking to build a 8xGTX580 render PC, since those are super cheap to buy second hand. But don't know how fast it would be.
Renders that I would produce wouldn't need to have high tech features and super realistic since those are for games.
For example here:
Difference is massive in 2 and a half minute gpus render 55 frames while cpu just 2?
I would like to see the best cpu render against best gpu render comparison, same project and very similar settings.