You could do something like this:
foreach ($c in get-content filerlist.txt){connect-nacontroller $c -cred $cred;invoke-nassh "software get http://<http server>/<ontapversion>.tgz"}
If you're in a Windows environment and don't have an HTTP Server available, Install IIS > World Wide Web Services on a server or workstation. Place the .tgz file in C:\inetpub\wwwroot\