If your looking for some modern day rock/metal to listen to, there is definitively some detailed stuff out there that will test your equipment and ears. A few examples are In Flames, Soilwork, Opeth, Into Eternity, Tool, Children of Bodom, just to name a few. Just make sure you get them in FLAC or a high bitrate. Though it may be "loud", the productions are heavily layerd with harmonies, keyboards, ambient noises, etc...
If you really want some detailed electronic stuff, Id recommend Shpongle, Infected Mushroom, The Infinity Project, Deep Forest, The Postal Service, etc...