Remote shutdown on OS 6?

This is a little bit late, but here's how to do it in PowerShell 3+:

$Hostname = "readynas"
$Username = "username"
$Password = ConvertTo-SecureString "password" -AsPlainText -Force
$Credential = New-Object System.Management.Automation.PSCredential($Username, $Password)
$Headers = @{ "Content-Type" = "application/x-www-form-urlencoded"; "X-Requested-With" = "XMLHttpRequest" }
$Xml = '<?xml version="1.0" encoding="UTF-8"?><xs:nml xmlns:xs="http://www.netgear.com/protocol/transaction/NMLSchema-0.9" xmlns="urn:netgear:nas:readynasd" src="dpv_1368497621000" dst="nas"><xs:transaction id="njl_id_1278"><xs:custom id="njl_id_1277" name="Halt" resource-id="Shutdown" resource-type="System"><Shutdown halt="true" fsck="false"/></xs:custom></xs:transaction></xs:nml>'
$Uri = "https://$Hostname/dbbroker"

Add-Type @"
    using System.Net;
    using System.Security.Cryptography.X509Certificates;
    public class TrustAllCertsPolicy : ICertificatePolicy {
        public bool CheckValidationResult(
            ServicePoint srvPoint, X509Certificate certificate,
            WebRequest request, int certificateProblem) {
            return true;
        }
    }
"@

[System.Net.ServicePointManager]::CertificatePolicy = New-Object TrustAllCertsPolicy

Invoke-RestMethod -Credential $Credential -Headers $Headers -Uri $Uri -Method Post -Body $Xml