here are some answers from Hans on his website :
A Quick Summary
If your Amiga has a PCIe slot, then it is recommended to choose a mid to high-end Radeon HD 5000+ series card
When choosing a card for the Sam 460ex, be mindful that the PCI slot is right next to the 4x PCIe slot. Choose a card that takes up only a single slot, and does not have an oversized heat-sync/fan that would block use of the PCI adjacent slot
A1-XE motherboards with the DMA fix and uA1 motherboards require disabling DMA for the IDE drives and USB in order to use any PCI graphics card (in the 33 MHz slot)
Radeon HD cards (and Radeon X1000 cards) do not work in the Pegasos-II
These graphics do not work in Classic Amigas
The drivers will eventually be able to use the full amount of VRAM that these cards have
The ultimate choice in card is up to you. Whatever you choose, enjoy
http://hdrlab.org.nz/projects/amiga-o ... ndations-for-amigaos-4-x/