Hi,
I owned a C64 back in its hay day and WOW what a puter ;-)
However other than emulating it (which I haven't yet done) running an ATX tower one would not appeal to me (unless someone gave me one!).
Power to the enthusiasts but I feel the Amiga is the farthest viable solution to upgrade.
Hey, if your made of money who wouldn't want an ATX C64 sat there with their others??