A towered A1200 with a PowerPC accelerator card has a much smaller PowerPC chip than is used in the AmigaOne series. The AmigaOne was sold by Eyetech but is discontinued.
The Pegasos 2 was also discontinued but, unlike the classic PowerPC version of AmigaOS 4, MorphOS classic is a freely available download. MorphOS runs some PowerPC Amiga software and a lot of classic Amiga software as well.
The current hardware capable of running MorphOS is the Efika computer from Genesi. It is a tiny thing with 128 megs of RAM that has a slower PowerPC chip but it will still run circles around a towered A1200 with an '030.
The biggest problems with AmigaOS 4 and MorphOS is that, unless you're running the classic versions on an accelerator card on an A1200/4000, you'll have to run an emulator like EUAE to get the old software to work.
For more information about MorphOS see
MorphZone and to see more information about AmigaOS 4 see
AmigaWorld or
Amigans websites.