Just received my T50rp's yesterday, they sound pretty good and I've begun collecting materials for modding. The one thing I have been unable to find is the paxmate or acoustipack damping material without having to order it from the internet. I was happy to find the Silverstone Acoustic Foam listed on Fry's website for only $12.95 and don't have to worry about shipping with having a Fry's local to where I live. So if you have a Fry's and a Michaels in your area you're good to go.
Fry's might also have Dynamat (though marked up a lot), which you could potentially use under the silverstone foam.