Well yer better off now than before, all depends on what kind of crzy insulation you got going on up there, because now you can start from up there, your drywall should just end and the insulation begin, don't fall through.
Basically it's just finding some way of hanging the speakers from the ceiling, since it's drywall, i'd suggest using one of these:

or something in this list
http://www.standsandmounts.com/index.asp?PageAction=VIEWCATS&Category=227And hang the speakers from the ceiling, if it would look alright. You could get fancy and recess the speakers and put cloth covers on it,
painted to
match whatever colour the ceiling is, depends on how fancy schmancy you want it to be.
Depends on what kind of insulation is in your wall...You may just have to get a plastic cable cover or some dowling and plywood to make a channel for the cables to come down from the ceiling and paint it the same colour as the wall. May not be too big of an issue since usually there is a big old TV in the way to cover up most of it.

If you're lucky you can run wires through your ventilation system.
I have no idea hw your room is set up and all of this may be totally useless.

Something like that could be an option, if there are no doors in the way and you have big floor speakers, and your house is all dreamy.
Disclaimer, I am not a certified carpainter, nor do I work for any companies I have listed/shown products from. Wear some kind of breathing thingy when going into your attic, unless you are a smoker, then yer dead anyways heh.