You can use synaptic, but the big disadvantage: it doesn't differ between updates and security updates and it cannot try to solve violated dependencies. Within Knoppix I would never do a simple update because the different version problem, and sometimes also security updates are difficult or impossible for this reason. For example try to install the security update of pidgin.

Within MX-14 I can also see different versions under package > force version for "ntpdate". Perhaps you have to reload the package list.

Why not mention MX-14? It is a very nice and little Live system and also suitable for HD installation. With the HD installation of MX-14 you have not the problems which you get with a HD installation of Knoppix.