I'd take Vieri, Cassano, Diva and Mico. Cassano and Mica could play other positions (behind the strikers, mico on the right wing) so I think they would be enough, but not too much. Alex is not neccessary
IMO Cassano is one, one and a half years better than Miccoli. What that means is that in a year or year and a half Miccoli will be as good as Cassano is now.