Location for Watcher Node

Hello,

I am trying to install some modules locally http://operatingquadrant.com/2009/08/22/webmon-a-scom-management-pack-for-basic-web-site-monitoring-configured-with-a-single-xml-file-part-i/ on the watcher nodes, but how to decide which servers are the best watcher nodes for the web site I am trying to monitor?

Some sites are hosted by the enterprise SharePoint environment (7 servers : AP1 (application); AP2 (application); FE1 (front-end); FE2 (front-end); IN1 (Index); SQL1 (SQL Cluster node1); SQL2 (SQL Cluster node2).

What should be the best watchers?

Thanks,
DOm

System Center Operations Manager 2007 / System Center Configuration Manager 2007 R2 / Forefront Client Security / Forefront Identity Manager