Currently I cannot say whether this configuration does surround or LFE. I do, however, get two channel music output from the surround speakers (in addition to the front ones) by enabling Duplicate front with alsamixer, so they do work, but I've yet to find proper documentation on exactly what this feature does; I suspect it might just set the rear speakers to repeat whatever is played on the front ones.

I need a test sound with identifiable output coming from each speaker in turn, just as the Nvidia Windows driver configuration app test sound does.