Room addition for a dedicated home theatre room...

[Zaphod]

OK here is a question that I have been thinking about lately and have no idea where to start. I want to make a room addition onto my house for a dedicated home theatre room. Now as far as building this addition goes, I have no skills in this. Meaning I would have no idea how to add a room from either the ground up for a ground floor or cut out part of the roof and add a 1/2 story onto my existing floor plan.

Now once the framework of said room is in place (i.e. exterior walls, roof, framing, electrical, plumbing and duct work), I know enough to actually fininsh the room to my liking from insulation to drywall, to what ever I want to do from the walls in for the theatre part.

My question is how much is this going to cost per square foot approximately to lay the foundation and build a unfinished room from the ground level. Also likewise how much would this cost to add ontop of my exisitng floor plan as a second story, including the roof, electrical, plumbing, and duct work.

Has anyone on this forum ever undertaken such a project, and if so did you do the majority of it yourself (excluding the actual building of the unfinished room)? Do I know what I am getting into? Also if anyone has any good links or resources let me know. Thank you in advance.