The 690 is a very .. very old card already .. and I didn't buy it for crypto mining but rendering.
My point is that it sux that my old card has after so much time till more cuda cores than any new you can buy.
And the Titan Z.. well ..who in the right mind will buy that one!? I wonder if they every sell one such card for the price they dream. So forget about that one.
The 690 was in the price range of a normal card back then.
just comparing the core, doesn't necessarily help here.
If you compare for example the 2880 core of the 780ti to the 640cores, the 780ti has 4.5x more cores.
However in terms of performance in crypto it is rather 2.5x the hashrate of the 750ti.
So basically it is like the 750ti had 1150core Kepler core
So the card with 2500 would rather be in kepler equivalent core something like 4492core (at this is what I hope...)
ie 50% faster than a 780ti