My question is simple, if i have a 5.1 speaker system on my pc (and supported by the motherboard / soundcart off course), can i direct from pd what to send to each speaker & subwoofer separately ?

(ps1/ I 'm asking cause i don 't have and cannot try it)
(ps2/ A "Yes" or "No" answer is ok, just to know)

Yes (use [dac~ 1 2 3 4 5] and assign the number of outputs you want to use in the audio setup dialog).