Re the 2012 / 2008 question. Yes, you can use a SQL 2012 MSX server and enlist 2008 R1 and R2 and SQL 2005 servers if you have those still. Obviously be aware of using 2008 or above features in jobs that will target 2005 servers. These will not work. What works quite well is to create Target server groups, see BOL for detail. You could then create a 2005 group if this is an issue. You can also populate your Target server groups from a SQL CMS server which may have groups defined in it.