Dynamat is good stuff so long as you can get it for the right price.
Now keep in mind sound deadener will help with the structural borne sound, but won't have much effect for the airborne, i.e. exhaust, tire, road, etc. Hints why use of a multi layer combination of CLD and MLV is the way to go.
And yes I hate doing things (be it car repair, installation, etc.) more than once. Do it once with quality materials/parts and call it a day.