Your propositions are way too expensive. You get a decent PC with lots of software for that price. The way for a new Amiga is either a high end gaming console, or a low end mobile platform/netbook. Nothing beats PC these days, when you want the most bang for the buck.
EDIT: To set this straight: Amiga is not coming back. I meant an Amiga substitute.
All modern consoles run on PowerPC derivatives, btw. Many super computers run with PowerPC. There is nothing wrong about the platform. It is just that Intel has a monopoly in the desktop market.
I think with pervasive computing there is much space between Windows and Unix for a compact, easy and robust OS. (Oh, I like Linux and such, but I don't believe in "one size fits all".)