@Dave Melton from what I have seen, the Kitchen cabinet companies that you can buy premise cabinets from, are also getting you knock down cabinets, that have been assembled already.

Here are a few links to check out.Similar topic:https://www.biggerpockets.com/forums/84/topics/417166-soundproofing-apartment-recommendations---help-neededProduct resource:  Look at page 67 (figure 156) or so with floor assemblies. https://www.nationalgypsum.com/file/THESOUNDBOOK.pdfProduct resource:http://www.kineticshometheater.com/isolation.htmlhttp://www.kineticsnoise.com/ As for the foam @Jd Martin mention, know the different between "open-cell" vs "closed-cell" foams. 

"NOTE: We've assembled several comprehensive guides that revolve around landlording.

There are several important things you need to be successful in real estate, one of which is a great team. I'm going to talk briefly about who should be on the winning team (this post got lost somehow, and I felt it i...

What I learned is that if you plan your fix correctly so all the fitting line up and mate properly and clean/prep everything very well before assembly.

Did you buy them assembled or flat packed?

Your post reads as though you are not quite ready to assemble a real estate deal on your own.

"NOTE: We've assembled several comprehensive guides that revolve around landlording.

They tell you that you need to assemble a team.  

I always tell new investors to focus on people first - if you need to work with a turnkey outfit, or even a self-assembled team, you need to have people you trust to be transparent and ethical.