Kubuntu and Ubuntu are the same thing, the only different is the GUI(graphical user interface) Ubuntu uses Gnome and Kubuntu uses KDE, Xubuntu uses Xfce, they are all the same system just with different GUI. It would be a lot easier to just install the DE(Desktop Environment)/GUI you prefer, and by the way you can have as many DE/GUI you want there are many available for Linux, you can choose which one you want to use at the login screen. Here one useful link: http://xwinman.org/
Originally Posted by Piyush M
... If I install kubuntu 9.10 then do I need to update too much?
Yes you would to do several updates plus the system upgrade, it would be a huge step back, it is way better if you wait 2 more months for Ubuntu 12.04, if you want to reinstall the whole system.