Transfer Files via Firewire

• Boot one of the Macs (preferably the lesser model) as a firewire target disk.

All you have to do is connect the two Macs via a firewire cable, boot the master (preferably the higher model), then boot the other and hold down the t key until you see a blue screen with a yellow firewire symbol. This Mac will now appear as a normal firewire hard disk on the master's desktop.

Ref: How to use FireWire target disk mode

Transfer files: IP over FireWire