The cheapest way seems to be the Phantom running the whole Falcon board at 25 mhz.
There'll be a new version out this year and it should cost less than 50 Euros as I've heard.
The fastest Falcon I've heard of has 105 mhz iirc and is run by Didiér Méquignon (right spelling?), author of aniplayer.
I know of some person who did want to try up to 150 mhz on his CT60 but unfortunately I did not get any results about that and he meanwhile sold his Atari bits.
I saw his machine running at 60 or 66 mhz.
