I find this thread right now.
It would be nice a new Atari clone based on modern system.
Anyway, I don't thik standard hardware pc is the right solution. In my opinion at the moment the best option is an ARM platform, like those of the upcaming netbooks.
Of course we would need a port of Mint/Xaes-MyAES to the new architecture or imagine (at first) a solution like Aranym: an hidden linux lier on which build a custom version of Aranym or something like that.
With optimised applications we could have enough power and flexibility to build a modern system.