My question is pretty simple. I have Ubuntu 12.04 with Unity and I want to login with KDE.

I have seen recommendations to:

1- run the three commands:
$ sudo add-apt-repository ppa:kubuntu-ppa/backports
$ sudo apt-get update
$ sudo apt-get install kubuntu-desktop

2- run just the command:
$ sudo apt-get install kubuntu-desktop

3- run the command:
$ sudo apt-get install kde-standard

4- run the command:
$ sudo apt-get install kde-full

5- run the command:
$ sudo apt-get install plasma-desktop

6- run the command:
$ sudo apt-get install kde-plasma-desktop

7- etc ...

This question is very related to this one, but the answer there is not clear enough to me. There seems to be quite a number of quasi-identical commands one could use to install the KDE desktop.

I just want the desktop, no KDE apps since I'll just use the ones I'm already using in Unity. Of course I also want the needed repositories added so the KDE desktop will be kept updated.

How would I go about doing that?