Hopefully I'm going to have some money to buy a new machine fairly soon. Much of my work is sample based. I have a small network of machines, using ViennaEnsemblePro to drive all my plugins, and return audio to my DAW.
Ideally I'd like to make my main machine a laptop, running nothing but the DAW, with the sample players continuing to be on desktops. That way I could plug it into the network to write sample based stuff, but also take it away and work on synth-based stuff while I'm on the move.
The problem is I don't know much about laptops and audio interfaces. As I understand it USB and Firewire are both considerably slower than PCI, which, on top of the latency caused by passing MIDI and audio across the network, is going to cause issues.
...Probably going with an SSD hadrive could be very helpful...
I second that, just got an SSD in my laptop and it screams, comparatively (albeit it's just my business computer), but it's a pretty beefy laptop (~$2500). But getting the SSD was like getting a new computer.
I ran my macbook pro as a sample slave for a long time, it performed quite well for me. Like the others, the most important thing is that you have a screaming hard drive to access those samples as efficiently and quickly as possible.
If your laptop has a ExpressCard slot, then it could be the best option to get a ExpressCard audio card, I think. Although there are very few to choose, quite expensive RME products or cheap but a little bit restricted Indigo IOx.
I prefer CardBus(or ExpressCard) to USB on Windows laptop from my experience.
At the moment, I'm using 2 laptops with the VEpro. One for DAW and notation, one for heavy sample based VSTis such as VSL SE, VSL Solo strings, Garritan Steinway, etc..
If you are going to run all the samples internaly on your desktop then you don't necessarily need a SSD on your laptop, I think.