I have a pair of Panasonic RP-HTX7's. They're pretty cheap and sound okay but I'm looking to upgrade sometime in the nearish future (fall/winter). How comfortable are these headphones when used for hours (I'm talking 8 hours or more)? They look great, and they look comfortable. One of my friends has them and he says they sound amazing but really need to run through a portable preamp or amp. What do you guys think? And which amp is best, and preferably portable.?