Since Beats are closed headphones (as far as I know!), you should look into the mods done on other closed headphones. Similar concepts can be applied to these Fake Beats you found.
If you look around the Forum > Equipment Forums > Headphones (full-size), you will find that many of the longest threads actually contain A LOT of modding information. This is especially true of the Orthodynamic Roundup page (although not -all- information here can be applied to the Beats since the driver type is difference). Depends how far you want to go.
Though some of the basic materials you can try for some easy, preliminary and reversible mods are blue tack and/or plasticine (non-drying modeling clay), cotton and porous materials like felt or sponge or the synthetic likes. Also remember that if you heard of any mod for speakers or for car audio systems, you can take part of it or change it to apply them to headphones!
**EDIT**
whoops fail. Of course I missed the line about changing drivers 
like THE KEYWORD of the whole darn thread! Sorry 
Start by finding out the size of the drivers as well as how much room you have to mess around with it. Only changing the driver will not solve everything. Well, sometimes, but not likely.
Edited by kalbee - 2/29/12 at 7:35pm
