Interesting, never heard of them. According to [1] you need an amp to drive them though - is that incorrect? In which case they aren't quite equivalent to V-Modas that you can just attach to your whatever-mobile-device, are they?
They have very low impedance, so you can use them without an amp. Hope you see this in time. OTOH I really recommend you buy the AKG velour pads instead of using the stock ones.
[1] http://www.head-fi.org/t/485039/superlux-hd668b-are-they-rea...