Hi, the question is quite old, but in case other people would be interested.
what you can do is to use Kscreensavers into Xscreensaver. For this select the Kscreensavers that you like - you can display these with 'ls /usr/bin/*.kss' - then copy (as root) those you prefer into the xscreensaver directory which is /usr/lib/xscreensaver/ (or maybe /usr/local/lib/xscreensaver/) (to select those you wish you can run those in standalone, for example $ /usr/bin/ksolarwinds.kss)
Then edit the file ~/.xscreensaver and follow how other GL screensaver are written to add a new line for each new screensaveer.
thats it!