Mac Mini:
2.1
2.4
The mini could get a 2.1 only option, with super drive, RAM, and HD separating the models.
iMac:
2.1, 2.5, 2.8
If apple wants to make it smacked up against each other like the MBP which i think is ridiculous, then its 2.4, 2.6, and 2.8
But right now, its hard, there is this huge gap between 2.1 and 2.4, so most of the decision making process will be 2.4-2.8.