That's were I got mine...Home Depot. I think I paid 2.25 for a 12ft length. Much cheaper than I thought. After installing it, I thought of a few way to make it easier.
I had trouble getting the dry wall screws to "bite" into the the RC. This resulted in the head of the screw not sinking into the drywall. I would think that after the RC is up that you could install wood furring strips onto the RC. In a perpendicular fashion. It would look like a grid. Then install the drywall and screw it into the furring strip.
I managed to get mine to work without the strips. A while ago I posted some layouts for my room. Well, we are in the final stages now. All that's left is the waines coating and installing the solid wood door with the threashold and weather stripping around it. The room won't be sound proof, but it should be fine for my modest setup. I'll post some pics once we are done.
Buck