I am new to the EZ drummer 2, i am having a hard time figuring out the difference between Midi packs and the EZx .. Take for example the rock solid EZX and the Rock solid midi pack why would i but one over the other ?? I have purchased the Rock solid EZX and love it but if im going to add to my arsenal why would i but the Midi packs.. Sorry i know this may sound stupid please if someone could enlighten me on the two… Thank You