The head at the third photo confuses me, have you made any dissections? It looks to me like a species from the family Eunicidae, although I could be tricked from the photos' angle. Can you please upload microscope photos of an anterior and a posterior foot (where the setae are visible and clear)?
It looks like a Nephtyidae to me although I think I can see some black aciculae/chaetae which I've never seen before in the family... definitely needs a new series of photos I'm afraid.
I agree with some collegues. Considering the shape of the body and the parapodia it could be a Nephtyidae. However, a better quality picture of the prostomium would be necessary to confirm the family.