the ideal would be to get the neck back into correct postion, so no arteries or veins are constricted by subluxations, rotations; so then blood can flow properly. All a collar would do is hold you in a fairly rigid position, it would not correct anything. Neck is meant to be mobile.
I have had neck injuries, and pain, and bad posture for years, including last few years too many hours at PC--and wake up with neck and head in very weird angles. This past year, have been seeing chiropractor who adjusted rotated atlas-- and doing neck exercises (painful and hard to do at first, now quite okay), and my neck and head feel better than in many, many years! And starting to wake up with head in an okay position! (ie, not twisted angle)--part of that might be due to now sleeping in the inclined bed positon (for past 1 1/2 months).
link to info on adjusting atlas, and importance of this:
http://www.youtube.com/watch?v=2Ae5CHyS ... re=related
this video is of the orthogonal machine that does the adjusting--but a good chiropractor can do it with manual adjustments, and this way it costs considerably less.