Well i went to clark rubber and after discussing my issue with the sale assistant, went for the acoustic foam.
Its 50mm thick so it doesnt take up much room in the boot, and it doesnt hurt that its the only foam they have that isnt yellow or blue
The acoustic foam is slightly dearer but not much.. it was only about $30 dearer than the other style of foam.
Long story short though, it definitely makes a big difference! You can still hear the exhaust, but its only about half as loud as without the acoustic foam.. and its not an echoey sound like it used to be.