You can get a felt underlay that has a foil side that is made to put under wood floors, I think it would work well under vinyl. Two way carpet tape around the edges works and it is stickier than Moose snot. Homedepot.ca has it, "Silver Lining Plus Acoustical Underlayment" If you want some aditional acoustic underlay simular to Dynamat try "Resisto Self-adhesive membrane composed of SBS modified bitumen. Aluminum on one side UV resistant. Reflects heat." Rona and Homehardware have it at a fraction of the price of Dynamat.Put it under the Felt it's only 2mm thick.
That will insulate and keep things nice a quiet.
