Tronman nailed it.

The Mac Mini would be the most powerful system out there today to run MorphOS. Mac Mini CPU was G4 1.25 to 1.5Ghz. RAM 256 or 512 MB ( upgradeable to 1 GB ). Can easily find and buy used PPC Minis and less expensive.

It is impossible to find PEG II motherboards and pricey when they are up for sale. Mac Mini is the better choice in my books, gives modern, more powerful hardware with lower used cost.

I believe they scraped the dual core processor PEG III based off Freescale 8641D. Maybe would be too expensive? Or too little demand for it? Instead it seems they are working on a newer Efika with Freescale 8610 ( e600 single core ); top speed of 1.33Ghz.
http://www.powerdeveloper.org/program/