Site Servers and Subnetworks

We are still planning and deploying Altiris and I have some questions.   In one physical building, the LAN is subnetted into 5 different networks.  I have run into a problem with Wake on Lan and Multicasting across those VLANs.  My supervisor suggested we create a site server for each network.  Does Symantec have a best practice on this?  In other words, is it recommended to a site server for each network or do I spend my time on the Cisco side getting multicasting, etc. working?  Thanks.