XML : Inserting a new node into XML with PowerShell

I have an XML schema that I'm trying to insert new nodes into:

  <clusters>    <cluster>      <name>        cfcluster      </name>      <port>        45564      </port>      <sessionreplication>        true      </sessionreplication>      <server>        cfusion1      </server>      <server>        cfusion2      </server>      <stickysession>        true      </stickysession>    </cluster>  </clusters>    

I'm trying to write a script that has a new sever value, will check it against existing ones, then insert the new one after existing ones if it isn't found. Say for example I have a new server value cfusion3, I'd want my new output to end up like this:

  <clusters>    <cluster>      <name>        cfcluster      </name>      <port>        45564      </port>      <sessionreplication>        true      </sessionreplication>      <server>        cfusion1      </server>      <server>        cfusion2      </server>      <server>        cfusion3      </server>      <stickysession>        true      </stickysession>    </cluster>  </clusters>    

Assuming I have the xml stored in $clusterData and the new server I want to insert is stored in $cfInstance.name, I was thinking I'd use something like this, but can't get it working...

  if (-not ($clusterData.clusters.cluster.server -match $cfInstance.name)) {      $oldServer = ($clusterData | Select-Xml '/clusters/cluster/server').get_node()      $newServer = $clusterData.CreateElement("server")      $newServer.InnerText = $cfInstance.name      $clusterData.InsertAfter($newServer, $oldServer)  }    

I'm pretty sure the problem is that $oldServer is getting all nodes and I'm not sure how to modify the xpath to get just one. I've tried Select-Xml -Xml $clusterData -XPath "clusters/cluster/server[text()='cfusion2']", but that doesn't return anything. Any suggestions?