|Nvidia's Quadro K5000|
The previous Mac compatible card was the Quadro 4000, which had 2GB of RAM, 256 CUDA cores and a memory bandwidth of 90GB/s
By comparison, the new Kepler based K5000 has 4GB of RAM, 1536 CUDA cores (!) and a memory bandwidth of 173 GB/s.
Now obviously this kind of performance doesn't come cheap and the K5000 has a list price of $2,250 dollars.
When you consider the price of a fully specced Mac Pro for editing or 3D that's not too bad (of course cheapskates like me can continue to use cards aimed at gamers :-)
The K5000 can also be paired with a Tesla card to create a real GPU computing powerhouse called "Maximus" :-)
Click here for more info on the K5000 from Nvidia.
Or here if you want to know how to get better performance on the cheap.