Sound proofing units

[Amy A.]

I recently purchased a 12 unit building which I would like to take from class C+ to class B+. There are two 3 bedroom units on the second floor and the rest are 2 bedrooms.  I was just given notice (for November, not great timing) that the two units below the 3 bedroom units are moving out.  The noisy kids upstairs are a factor.  The 3 bedroom units will probably always have kids, so this will continue to increase my turnover.  I am considering sound-proofing the lower units by adding a product called QuietRock to the ceiling and shared walls.  Has anybody used this or is there a less expensive product you know of?  The ceilings need work anyway.