Just a couple of quick questions regarding subs constructed from Sonotube. -What is the actual material of the sonotube? (dense cardboard?) -Is it possible to use this type of sub as an endtable? Meaning, would I be able to have stuff sit on top without falling off? (ie Pictures, etc) -Do most people run external power to these subs? I know that in cube designs you can simply mount the plate amp into the side, but on a sonosub design mounting a plate to the cylinder side would prove quite dificult. Thanks for the help in advance.