Jung used the word libido in pretty much the same manner as we today speak of action potential in neuropsychology
http://en.wikipedia.org/wiki/Action_potential , expect its noted today that its the same thing that happens in everywhere in our bodies, while jung saw it only a mental energy.
Well the definition of complex is "clusters of feeling toned associations around a common theme". If you think about money for example and think it as the theme and all feeling toned memories you have about money as the associations around it, the first time you had a summer job and was able to buy your first car, when you were little and figured out that you can change money to candy etc etc. Now because of these associations you have developed over the years aroun money is what makes you see money as something else than just a piece of fancy paper. People often think at complex as something negative, which it naturally can be, but isnt it always. It is more prone of being negative because negative things are more easily repressed and repressed things form complexes easier.
These complexes wont morph themselves into archetypes, but you are able to make archetypal associations around some theme, which forms an complex. Im not sure if its neccesary for archetype to have an complex to link itself to in order to have an effect, but that certainly makes the effect of the archetype stronger.
Its not that complexes become a channel, but because there are loads of associations around the theme(which together makes the complex), the complex has more energy than a single thought and can even seem to have its own energy.