I picked up a used pair of the U6t and they arrived a couple days ago, so these are my impressions after about 6-8 hours of listening to them (so take my opinions with a grain of salt). As background, I am more of a headphone guy and this is only my third pair of IEMs (so take my opinions with a grain of salt). I listened to them using either my iPhone with the apple dongle or with the FiiO Q5S. They are powered well off of the apple dongle and I didn't notice a difference. All of my listening has been with the m15 apex module. These are fantastic...