About PPC future and next (after X1000) CPU to use, forget the QorlQ 40x0 or even the 50x0 series.

Why?

Simply put our next CPU is the Altivec equipped PA6T and by the time a new machine will be needed (2 years after the X1000 launch, or more) the next gen QorlQ CPUs will be already available, check THIS for a glimpse.

They might make up to 8 cores variants and judjing from the past/roadmap the maximum Mhz count will rise yet again (probably to 3.0Ghz).
Soon AmigaOS will have Gallium and by that time (not now) Gallium will have OpenCL (http://cgit.freedesktop.org/mesa/clover/), who knows maybe even interesting NG X-cores will be out.

Of course it all depends on how things turn out today, if the X1000 shows promise to its investors there might be more money on the table in the future, otherwise there will be not.

Still, with the potential of a highly clocked Altivec equipped 8 core CPU (60x0?), OpenCL enabled Gallium, Powerful GPUs and even possible clusters of NG x-cores, if the money will be there to make such a system, I don't think we will be lamenting any lack of perfomance.

As for the price, it will depend on the production scale and how much money investors will bring to the table.

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SamFlex Complete 800Mhz System + AmigaOS 4.1 Update 4
Amiga 2000 DKB 2MB ChipRam GVP G-Force040 Picasso 2 OS3.9 BB2
AmigaCD 32