Insulation

My Basement Concrete Form wall already has insulation of approx. 3 1/3 inches over the concrete form walls. This insulation has a white vapor barrier. I want to put in a 2 X 4 Stud wall and insulate with rolled R-21. Should I remove the insulation on the Concrete form wall and then build the stud wall or just leave the current insulation and build the wall and insulate it also? I live in Colorado Springs, Basement is heated, very low humidity, basement is dry, no unusual problems, just basement is cold in the winter.

I am in the process of remodeling a basement and have a new stud wall in place. It is set in from the concrete wall by one inch. I have a few windows and glass block areas that are set into the existing concrete wall that I need to figure out how to finish. I would like to wrap the sheet rock to the window on the top and sides and use a wood sill. The concrete walls are 9 inches thick so with the stud wall, air space, and concrete the sill as well as the top and sides would be 8 to 9 inches wide. (Is the correct term for the area between the finished wall and the window jamp a "stop"?) I am wondering how to best support the sheet rock against the concrete. There would be about a 1/8" gap between the sheet rock and concrete since I made the new stud wall opening slightly smaller than the concrete opening to allow for the variation in the concrete surface around the window. I was thinking of using some adjesive caulk to fill in the void. I would also leave room for caulk between the edge of the sheetrock and the window jamb. Secondly, ( or maybe firstly) is this the best treatment. The basement is dry but I do not want to create a situation where the sheetrock breaks down because it is near the glass where the humidity is higher and the potential for condensation greater. Is there another material that would work better and be compatible with the sheet rock walls? DavidJ