I am not aware of any volumisers for the Matrix - but there is a front LP reg mods like the Trinity which are meant to greatly help efficiency which you might mean.
According to the website of the guys who make them (aardvark) they don't do much, other than make the Mtrix look good. Which is more than enough reason to get some.
Check it out at this place!
I have seen volumisers on thematrixcenter, amd aardvark, I was just wondering if the gave any performance gain.. from what buddha says they are purely cosmetic.....
What you can do nick is run macroline from each place where the volumisers go in, use straight fittings and loop the line round, gives you a bit more volume/ balances pressures.