YaST (openSUSE, thus)
to expand on abyzthomas posts

• Xen is definitely an advanced feature;
  not advisable for GNU/Linux newbies
• openSUSE 12.1 now again comes with KDE3
  it is a port of Trinity Desktop Environment
  spares you the hassle of KDE4 (even though your hardware seems to be up to the challenge ) and remains in the spirit of Linux of old
  there is also a live CD @ TDE (based on a somewhat older Kubuntu release) that can be installed on a hard disk as well
• from my experience with Fremantle for nearly two years and openSUSE for nearly six years i have to say... deb is a manure all right and YaST is by far the best "control panel" you may wish for.
• rather then live CDs, i would suggest you download VirtualBox and give each distro a run for its money with an install.
  as you can use ISOs as CD / DVD in VirtualBox, the installation will go as a breeze (definitely with two or more HDs...) and it'll make it easier to "save your setup / preferences / bookmarks & all" over several sessions
  and you may even have several VMs / distros next to each other & compare them directly

may the force be with you