I have used the Parallax P8 Propeller CPU on several designs I have done.
8 core CPU
http://www.parallax.com/propeller/Very nice chip for the price and a lot of code available for use at
http://obex.parallax.com/ .
Works a lot like Jim said he would have liked. Core for Video, Core of CPU, core for IO etc etc.
They already have done a lot of SID and other commodore projects on them as well.
If anyone wants a P8 CPU to play with, let me know. I have a few sitting around! Just PM me.