Sound deadening

[CFster]

Looking to install some sound deadening material in the back of the GTO. Since I switched to hidden tail pipes the "drone" is increased.

I'm thinking of doing the trunk in Dynamat, along with a partition behind the rear seat. I understand Dynamat is primarily a heat and vibration blocker. I should install something on top of it yes?

What are your recommendations? I've seen a bunch of posts about Damplifier, but it appears the site is down and the owner hasn't visited this site since the beginning of last year.

Thanks,
-Colin