@AmiKit
Hyperion doesn't recommend the best card, they recommend what they seem to bo the minimum graphic card to enjoy the new graphic system of OS 4.1.
As usual, the more the better.
Regarding Gfx memory, take a 128 MB one, it will be ok (anyway a 256MB one will only show 128 MB under OS 4.1).
Even 64Mb would be enough to enjoy OS 4.1.
Graphic memory will be used for transparency, compositing, etc..
As usual, the more the better