If you're looking for an IEM that boasts one of the best soundstage at any price, features powerful, clean and quick bass with excellent control as well as a clear, open an articulate midrange and a well extended and engaging natural sounding treble then the FD5 is a no brainer! If you own a good copper cable I strongly suggest you plug it to the FD5 as it will be a more relaxed yet engaging listen and if you don't it's worth spending the extra money unless you enjoy a more energetic and brighter midrange. I would stick to the larger nozzle as the narrower brings most of the benefits a copper cable brings with the downside of making the soundstage smaller and penalizing the upper treble presence and the engaging lower treble.