Latest NVidia card I used does about 200MB/second in repainting screens. AGA machine like low-end 30Mhz A4000 does over 4MB/second easily. But that wasn't the point-- the point was emulating sprite hardware not raw drawing capability. If you have a sprite overlay on top of an image-- let's say a curtain of size 352*240 and you move the curtain, the Amiga does it in a few microseconds, whereas your graphics card will be repainting the screen and take much longer. I can compute the exact figure for you if you need it...
You wouldn't use sprites on a modern graphics card. You'd use a 2D, texture-mapped polygon. I don't know if any current emulator does that, but it seems like a reasonable approach. Even relatively ancient 3D cards supported texture sizes in line with Amiga sprite sizes. (Or not. The 3dfx Voodoo supported 256x256.) Google pixel and polygon fill rates for your graphics card if you're curious. Anyhow, on a current card with maximum texture sizes that exceed screen sizes, you could probably fill the screen with more virtual sprites than there are working Amigas in the world--dependent on your implementation, of course. :-P
