I should point out that the Atari Falcon has had a PowerPC accelerator in the past (don't know if its still made, or what PPC processor it had though).
It also offered a non-planar highcolour mode when the Amiga offered HAM-8 (more colours, but much harder to program). It also has DSP and 16 bit sound, so don't laugh too hard when you laugh at the "poor atari users".
They also have a "coldfire" effort.
Don't for one minute think we have a monopoly on the souped up "dead" machines.
For example, Nate Dannenburg has a C128 in a tower with a 16bit 20Mhz CPU upgrade (SuperCPU), 16 Mb RAM (Commodore REU), CD-Rom, 4Gb Hard disk, and a bunch of other goodies. Sadly his website is down now, but hopefully he'll put another one up soon.