The Ultimate Ears Reference Monitors (UERMs) are indeed quite nice. I admit that I'm relatively new to headphones/earphones. There is an adjustment to the music in the center of your head rather than projected as an image in front of you. The trade-off is more clarity and detail than these somewhat older ears have ever heard from speakers. My goal is to put together a high quality, semi-portable system for my serious 2-channel and hi-res listening. The UERMs are the first piece of that system. Why the UERMs rather than other custom in-ear monitors like the JH13s or ES5s? The simple answer was that I got a great deal on them. I would say that the reviews of the UERMs on Head-Fi are spot on; they are accurate and detailed without being sibilant or harsh. Bass is tight and well-defined, but on the lighter side. The UERMS are definitely not for bass heads. I have used the UERMs with an iphone 3GS (lossless ALAC), a 2009 TADAC dac/headamp, straight from a few laptops and most recently the iBasso dac/headamp. The quality of sound has been directly related to the quality of the dac and the recordings. The UERMs are very sensitive and don't really need separate amplification. The iphone with lossless files actually sounds quite good. With the exception of the iBasso D7, I have not had any noise issues with any source.