problem with your neighbors after moving in and living there for awhile. is the next door unit lived in already? if not then you might go back after closing the deal and add like 1x1 studs on top of the finished drywall wall and then cover those stud with drywall again. This will create an air gap between the two walls and help provide more soundproofing. Others on the forem may have additional suggestions. good luck and let us know how it turned out. LJ