Balanced cables make no difference for sound quality but some amps deliver more power over balanced port so they can make your headphones louder. Different pads will certainly affect the sound but do you really think that a random pair of cheap chinese pads is more suitable for your gear than what the engineers came up with during the designing and testing process? If you like your headphones then just use them the way they are and if you need more then upgrade to something else. Modding headphones seems like a waste of time and money mixed with a healthy dose of snake oil to me.