The more the better
As a MAC fan I like the mini but it depends on how small the setup will be. As with any computer recording setup, the more resources the better. The mini is limited on the memory upgrade (only up to 1GB). I have a G5 IMAC with a gig using a firepod and cubase and it can be challenged. I also have a G4 powerbook and have tried to use it as a portable setup but the G4 is just not powerful enough with 512 to do the job over 3-4 tracks.
If you are only talking about a couple of tracks over USB or Firewire then it may be ok. I don't think you will get much more than that without frustration.
Good luck.