Get XB500 they are MUCH MUCH better off when used without amp from a weak source like iPhone. In fact they are by far the easiest driven headphones among the 7 (HD212 Pro, AKG 518 DJ, K 181 DJ, XB500, XB700, ATH-M50 and DT770 Pro/80) bassheavy mid-fi closed headphones I've tried and also the bassiest, XB700 is like the 2nd hardest driven headphones among those, right after BeyerDynamic DT770 Pro/80 or they might be around the same actually. XB500 sounded near its full potential off an old Creative Zune MP3 player I like to test the headphones with to see how easy driven they are (I usually only listen from the comp though). AKG K 518 DJs aren't that bad either and they look awesome and are very portable but they are a lot more uncomfortable than XB500 and need overnight stretching or else the clamping force is far too tight, both headphones have extremely punchy bass but XB500 delivers more in the deep bass while the K 518 DJs have more upper bass focus that is "snappier", good for drum & bass music while XB500 does electronica, trance etc better. Both have smooth/dark sounding highs, they are prolly the closest to each other soundwise.