I have personally tried the Superlux HD668B AND Shure SRH440.

The SRH440 is light years ahead of the HD668B, both in sound quality and build quality.

The 440 is plasticky and cheap feeling. But it still feels like a chinese product made by a branded company. The 668B just feels like a cheap china product (those flimsy stuff that cost RM10 or so).

The 440 sounds boring and not engaging. Lacking warmth, thickness, extension and feel. It's not a bad headphone but U must like the sort of sound it produces. It does have bass (quite flat response), mids and highs (bit sibilant from what I can remember). Keep in mind that it is a monitoring earphone and therefore sounds like one.

The 668B just sounds like a wannabe product. It has super sharp piercing highs and LOTS of it. It is extremely sibilant and painful to listen to. The mids are pretty much nonexistent. I've never heard vocals so far away before. When I turned the volume up to hear the vocals, the sibilant, piercing highs comes and kill me. I can't even remember how the bass is like because the piercing highs are just too distracting. If you like that kind of sound, you'll love the 668B.

My recommendation is: If you live anywhere near Jaben, go try them out! Jaben has the 440 and although Jaben does not carry the 668B, they have a unit to try out. If you like how it sounds, wa-la! $$ saved.

Source for testing: HifiMan HM-601.

yea, most people like monitoring earphones somewhere in the middle of their audiophile journey. =)

after you get out of the audiophile state and start listening to ur music (not ur eq) then your sound preference changes drastically. =D

Ok, i try to summarize them by using my understanding.
SHURE SRH440- better sound clarity, smooth sound, lack of bass.
Superlux HD660- the best of all, superlux model stated, good bass, not so smooth sound, the sound tends to mix the high, and mid. but still better than mixstyle dj headphone that costs rm10.
ok, i thought the result was predictable.

Let me try to describe more music oreference. I like bass, and if the bass is BOOM it should sounds BOOM not BUUM or BUU or BOOB.
However, i also like rock music that really need to have better soundstage bcause i want to hear and differentiate all the instruments in it, the guitar, drums, bass, violin and bla bla..
I tried monster beat solo HD and studio. I Kinda like the sound, but from reading, some people said can get better with lower price range.
So, can anybody recommend me a Monster Beats Sudio-like sound headphone, but of course better. mybe with preamp. Thank you.
Btw price range is below 400. Thank you