There are plenty options.
Most advanced is the Pegasos.
MorphOS is very promising and the most advanced Amiga style OS running on the Quark kernel which is similar to QNX.
Regarding Linux the Pegasos is also leading with newest kernels available.
It also can run MOL OS-X.
The AmigaOne is similar to the Pegasos, only behind in all aspects.
AROS also looks very interesting.
Upgrading classic Amigas with PPC cards is much too expensive and they not classic anymore when upgraded. An AmigaOne or a Pegasos would be the better solution in this case IMHO.
