Mark,
Me again!
As I have just said else where, a middle ground product that you could consider is IHC, Intelligent Home Control. Which is also manufactured by the CBus manufacturer Schneider Electric.
Have a look at www.squared.co.uk for more details or let me know as I have the latest 2005 .pdf here.
One other consideration with the cat5e AV system is that the Nexus does not have to have all its sources based at node zero, just the nexus hub. The sources play into the nexus on cat5e just as the view or listen points play out.
Hope this is all helping.
Chris