What Midi/audio Interface For Pb G4?, for best performance on a Powerbook Options

[manexmachina]

I am trying to find ot what kind of power I could expect using a powerbook G4 for audio work. I'm going to be doing large film scores and some audio editing. I used to use ProTools, but I'd like to use DP, Logic, or Nuendo instead (for the midi capabilities). These are my questions:

1. What hardware would I use for a Powerbook G4 which would give me LOW/NO LATENCY. I'd like to have six outputs for 5.1, but don't need more than 1 or 2 inputs.

2. What kind of performance could I expect? Compared to, say, a dual 1.25ghz or a 2.5ghz PIII (for Nuendo).

thanks in advance.