Mmm, the hd sandwich is a project of Mike's (at least, the first one I ever saw). If you go and look under storage on the main page, I'm sure you can find it. He did a couple of revisions to it also, might be worth checking up, as well as the recentrubber block modding madness
. Something which I will resort to shortly as well.
There is, like you say, sound being absorbed when using metal plates, but not all of it, just certain ranges are effectively absorbed by the metal. Foam helps dampen it down some more, amongst other things.
Only you can decide how far you want to go, and how deep your pockets are (in terms of cash/how much you are willing to spend).
Also, you might want to check this
out, or the younger brother
of it. They are expensive though. But are quite pleasing in an aesthetic kind of way, while at the same time providing adequate cooling and noise dampening qualities.
I have no idea about the Tiger systems solution though, you may want to drop gtek a letter (presuming that's where you found it?), in regards to that question.