Phew, thought I would never live to see this day.
 
So, now I can officially consider myself a Doctoral candidate. Yay!

Hi Martin,
 
Thanks for the encouraging words regarding my exams!
 
As far as the problem with RME card is concerned, I think it can be easily resolved with the AEB-O connector (it worked for me). But since buying it is not an option, you should be able to play back through the SB PCI 128, although I think you need to create a plughw device in your .asoundrc in your $HOME dir (or alternately include it system-wide into /etc/asound.conf file) where your input would be RME card and your composite output your SB PCI card. I am not sure about the syntax for the .asoundrc scripting language (especially for this kind of setup) since its documentation is still a bit skimpy, but alsa-devel and alsa-user lists would be a good place to find out. Keep in mind, though that RME is a multi-channel card, while the SB PCI is stereo only (or 4-channel at best, can't remember any more -- I got rid of mine in favor of SB Live audiocard), so you will most likely be able to hear only one stereo feed at a time.
 
I am not sure this is the 100% possible solution, but theoretically (at least from what I recall about the .asoundrc stuff) it should be possible.
 
Hope this helps!
 
Ico