This is a great way of getting more out of each CPU, and not pricey these days.
I currently run 4 PCs on a Local Area Network (LAN), one with Nuendo, one with just plugins and virtual synths and Korg Oasys, one giga sampler and one Avid DVXpress Pro system.
All are linked via the cables and thus sharing files and the like between them is very simple. Also with the items shared each PC is running well below capacity which was essentially the point of the excercise.
HOWEVER you will likely have to invest in some near-silent Power Supplys and CPU fans as one PC is noisy enough - any more becomes troublesome.
Of course the audio computers are also linked by Midi for control.
If you run Windows XP it is even easier as it does most of the setup for you.
Good look with it.
Pauly