I got a PCMCIA Firewire 800 card for my laptop and a firewire 800 7200rpm external HD... totally bypass the internal hard drive.

Just one thought, I had problems connecting a Maxtor external harddisk WITH
my XL1S all through firewire on an older DELL laptop. I've since switched to
USB for the harddisk (the harddisk supports both USB & firewire) and just have
a camera on the firewire port. Works perfectly. For this I would recommend
to get an external drive with at least an USB(2) port, and if you want a
firewire (I would still use the USB2 port though).

p.s. there are also multi-channel audio systems for a LAPTOP (connecting
usually through USB as well), like from m-audio. So you could even plug the
laptop after a day of shooting in your home (audio) studio!