The Dell delivered Full giga polyphony with an external firewire drive.
Atmosphere/stylus/trilogy were a bit of a dissapointment in that regard.
They are clearly more CPU intensive and thus on the dell delivered less notes.
I figured that the dell with external drive plus an audio/midi box weighed about as much as my little shuttle case does. So the dell did not stay.
I am sure that by now there are some really thin pc laptops with big screens.
The key issue is having seperate controller chips for the firewire ports. At least a dedicated controller chip. Dell was completely unhelpful in being open about this info.
GPO will certainly not be a cpu hog. You should get a ton out of a laptop rig.