cryptonote... factor 3-4 over which cpu?
if we could reach 4-500h/s with a single 750ti it would be far more interessting than mining it with powerwasting R9 290x.
don't expect too much from the 750ti. Looking at the way the R9 290x works it uses around 3Gb of vram, so assuming it gets implemented in a similar way (which we will never know

) you won't get these sort of performance with the 750ti. This will certainly be also a problem for the 880.
But the titan Z should do very well

ok 4-500h/s was just a thought out into the blue... but if the 750ti could make 200h/s it would be more than interessting.
GPU's are easy to scale and use less energy.
but doesn't matter at all... I will be happy *sing* with everything crazy C&C will publish.