Firewire 800 Options

[bonzulu]

Hi, I'm running Cubase SX3 on a G4 Powerbook. The VST plugins are in the powerbook and the project folders (songs) are on a Maxtor external hard drive with FireWire 400. Every is fine till the project grows and starts to stutter or worse. I'm habituating holding the fx plugins to a minimum and the other standard CPU economizing procedures.
My question is twofold: 1- Does it make more sense to move the active projects into the powerbook for a session and only use the external HD for storage? and 2- Would a firewire 800 disk make a significant difference in stutter free/smooth data transfer? If yes to the second question, is it also sensible to store the larger VST libraries on a firewire 800 disk? The question boils down to- my understanding is that an internal (ATA?) drive is faster than and external disk (correct?) and if so,does firewire 800 significantly close the gap? Thank you in advance for any help in this regard, Bonzulu