I'm finally about to build my LAN, having bought the third machine in September. I won't have all my software for some time to come, and I should have another machine this September, but I want to start building as though those things were in place.
Here's my thoughts:-
I'll have four machines. The master machine is a quad core Intel, one slave will probably be similar, and the other two slaves are Pentium 4, 3Ghz. I have a lot of samples, but the real CPU/RAM hogs are the complete Vienna Instruments, East West Choirs, RA and the 7Seas Grand. I want to organise these in a way that will allow my normal workflow, whilst also getting the most out of the machines. At first I thought I would put the VI Strings on the master machine, because I use strings in most things, and they'd be available without turning on the whole network. But then I thought, if I'm running Cubase, and potentially video streaming, on that machine, and I want quite a lot of string articulations, I could be screwed. So now I'm thinking I'll put all the less commonly used stuff - such as the prepared piano, glasses, waterphone, etc - on the master machine, and put the instruments I'll use a lot on the slaves.
How much RAM does your master have? with 4 cores and a few GB of RAM you shouldn't experience huge amounts of trouble with strings only. Of course it does depend and I don't know VSL at all, but still I can't see how a "super" computer would crumble with Cubase and strings (and video). So, I really do see a point with what you say, Dave.
I have a setup similar to yours. I keep all my major libraries on external computers. And only use a few items -- Ivory and Stylus RMX, plus MachFive v2 and Kontakt 2 to host some loops or effects when I need them on a particular project.
The "orchestra" lives on external PCs. EWQL Symphonic Choir just is a beast, though; when you have full choirs with the wordbuilder full-on you really need at least one entire PC dedicated to it. But that depends on what you need to do.
Main advantage of keeping the main libraries external is that when you are streaming 'and' recording all your splits 'and' your midi template is 300 lines long 'and' streaming video 'and' you add one more delay or something in mixing on your DAW, you have a ton of overhead left.
Maybe I have too much at this stage, but it works very well.