Ubuntu Networking :: Setup The Most Efficient Way To Remotely Administer A System?

I am trying to setup the most efficient way to remotely administer an ubuntu system. So far I was successful in setting up ssh. I have the server running and made sure it only uses keys to authenticate and changed the default port. I can connect to the ssh-server. This system is behind nat and bots trying to break-in when I forwarded the port. I used the AllowUsers option, which helped in knocking back these rouge connections. I was not comfortable leaving a port open all the time, so I set up logmein Hamachi VPN and closed the ports that were open on NAT.

Now I use Hamachi and am very impressed. I use VNC in VPN. But Vino is slow, I tested x11vnc and it was slightly faster. I also tried to set up freenx but nxsetup file was missing. some one posted that file in the forums and suggested copying to the system but I was not sure if I want to download a script from the forum and use it. So for the time being, I thought I will just concentrate on X11vnc until freenx is fixed.

I would like to create a separate desktop on the server and use it to access remotely. This way we will not have to fight over the cursor (sounds funny but very frustrating). From what I understand x11vnc has this function inbuilt (uses vncserver). I cannot get it to work! when using ssh, at the remote machine's command prompt, if I type "evince xyz.pdf", it does not launch the "xyz.pdf". what am I doing wrong? When using VNC, how can I change between different users on the remote machines? Right now I can only use VNC in one account that I first setup. When I try to change to another user, vnc client goes blank. How can I get as much control of the remote system as possible? Right now I need someone to switch on the remote system and login to their account before I can VNC. Can I use ekiga inside VPN, I use skype right now and it's sometimes terrible with dropouts. I looked around and someone suggested using ekiga as it works very well over lan. How do set up ekiga so that I have a direct connection with the remote system? Is there any client that just takes the IP address and creates a connection? Mumble seems to be the popular choice, it's most suited to LANparties, I just need a connection between two systems. I am trying to set this up to help users with hardly any computer knowledge to use the system without any issues.