Hi, I've had the superlux 668b for a while now, and it is without a doubt one of my favorite headphones. I like it's neutral presentation and it's sparkle in the high and it's ability to reach to the deep lows. I want to now find a step up from these. I've searched the forums and most threads about the superlux usually are just people raving about how good these are (which I can understand) but no one really gives any indication of what sound signature these headphones mimic. I've been looking at the DT880 600ohm and I'm almost gonna pull the plug on them so anyone out there that can recommend me what i'm looking for. the budget is around $300.
I also have a hd650 paired with a LD MKIV so i'll be nice to find headphones that works well with that amp.
With a good OTL amp, you'll really enjoy them. Only major sacrifice might be that you'll lose the really low bass stuff. But I'm listening to Sublime right now through mine and it's pretty impactful. 
