Like fred said don't install puppy to the HD if you have any other os'es because it runs as root. The increased boot time isn't worth the risk of having one of your other HD installations compromised. It's a great Utility Disk, I keep one on had all the time, but I only use it as a tool. Not an OS. It could be a great portable OS, but my personal preference is what ever Live CD I have on hand. It's always changing because I end up giving them away. I really wouldn't want to give everybody a Puppy Disk.
One last quick note about puppy, it's based on slackware. Which has a whole different way of doing things than debian.
I wouldn't mind trying KDE to see what that's all about
You could install KDE desktop into just about any linux distro.
If you want to try different distros, I incourage you to. I personally have three distros on this laptop. MS, Linuxmint (debian base) and Vectorlinux (Slackware base). At home I have two desktops with no less than 6 distros installed at any given time. don't ask my to list them because they are always changing.
One good place to start looking for distros is http://www.distrowatch.com
they have a search engine where you can look for just what you want. For example I do a search for "live cd" they have 166 distros, puppy is number 118 alphabetically .
At distro watch you can read up on each one what they are supposed to do, what software they have, such as KDE and so on.
You mentioned in your other post, your just getting used to the command line, and you were dealing with a bug problem.
Taking both those into account, I'd suggest giving debian stable a try. for several reasons. You have some experience in Ubuntu/LinuxMint which is Debian based, except they both use software closer to the bleeding edge. Debian stable is VERY stable. I always have debian stable installed as one of my multi boot OSes, "Just because I can count on it". Another reason debian has a large community in their forums much larger than here or ubuntu, in fact most the people here and at ubuntu often go over there also. But folks who just use debian won't often come over here. And all your knowledge to date will apply to debian. Also what you learn there will apply here, soon you'l be rolling your own mix of the two much like the rest of us.
One last tidbit, in anther thread there was a hint that linuxmint is thinking about a debian based version.