There's lots of other posts that discuss this, but basically all you need to know is:
* AmigaOS 4 is still being developed for A1 and Classic.
* Hyperion can't release OS4 for other systems (e.g. Sam440) until the court case is finished.
So for now if you want to run the latest incarnation of OS4 your only options are classic (if you can find a PPC accelerator and have a second mortgage available to you) or A1 (ditto).
The sooner we get OS 4 on other hardware the better. In the meantime I'd look at AROS as that's progressing nicely, and does run on hardware like the SAM if you don't want to use a PC.
