> stick to a Radeon X1600, X1550, X1300 if you
> want full 2D/3D on MorphOS and 2D on Linux.

Aren't those cards 3D-supported on Linux? And why no X19x0?

> I don't know how well the Radeon HD 5450 is supported on Amiga OS 4.1

R3xx to R9xx is 2D-only in OS4.