I don't think that's possible, certainly not recommended at least. Generally with these control panels, you want to install them on a clean OS installation.
However, if you like Kloxo (hard to believe in my opinion), check out zPanel. As far as free control panels go, zPanel seems to be the only one I'd even consider touching.
Kloxo and webmin are absolute crap in my opinion.
Last, if you're only managing a few websites...why not go no control panel? Sounds like you already know what you're doing.