Bad assumption. First, I think the Efika's PCI slot is keyed to only accept 3V PCI cards. Also, for both PCI and AGP cards, the Efika simply won't boot with certain ones (because of BIOS issues I guess).
I went through my stack of video cards looking for one that would work:
S3 Trio 64 PCI - doesn't fit
S3 Virge DX PCI - doesn't fit
Cirrus Logic GD5464 PCI - Efika doesn't boot
SiS 6326 PCI - doesn't fit (supposedly supported by MorphOS)
SiS 6326 AGP - Efika doesn't boot (supposedly supported by MorphOS)
nVidia TNT AGP - Efika doesn't boot
nVidia TNT2 AGP - Efika doesn't boot
ATI Rage IIc AGP - Efika boots, but not supported by MorphOS
Matrox Millenium G250 AGP - Efika boots, but not supported by MorphOS