I've got XB500, and have briefly owned the LP2, the Q40 is a bit lesser in bass quantity but while both XB500 and LP2 sounds very bloated in bass like they'd be clouded in bass, the Q40 nearly hits with the same impact, great punch but a lot more textured in the bass than those before mentioned headphones. Let's say Q40 has bass where it needs to be to get a nice impact while XB500/LP2 sounds like having excess of it, doesn't add a lot to the impact but more covering the other range of the headphones.
Still a happy ZO2.1 + Q40 owner of about 2 years of use and wondering whichever config will be able to satisfy me more. :) Do note for me personally ZO2.1 is big part of the magic, I do have ZO2.3 as well but the ZO2.1 just pairs so much better with Q40 and making it very balanced in the mids & highs (it tickens up the midrange slightly and very gently smoothens out the highs) and with ZO2.3 it has a very slight V-shape sound to it, for me the mids lack that nice full-bodiness I get when using v2.1. I'm a never recovering basshead but I also care about the mids & highs as an enthusiast. Hard to get good balance of everything when you crave such a seriously boosted bass amount but Q40 + ZO2.1 gives me that. :) Of course it will also depend on what source is used, Q40 is so far the most picky headphone I've used regarding what source and amp it's paired with, it really changes sound signature very easily depending on the equipment and it's not a cheap vs expensive thing...
To give you an idea....
SoundBlaster ZxR + ZO2.1 + Q40 = Pretty bad, too warm, overly smooth, somewhat muddy bass
SoundBlaster ZxR + ZO2.3 + Q40 = Pretty good, good tonality (= realistic mids/highs balance), great detail in mids/vocals, slight lack of "extreme punchiness" in the bass I love
Realtek ALC1150 with onboard TI NE5532 amps + ZO2.3 + Q40 = So-so, overly analytical, bright, slight V-shape, slightly lacking punch in the bass for my taste and that fullbodied up-front midrange I like
Realtek ALC1150 with onboard TI NE5532 amps + ZO2.1 + Q40 = AWESOME, extremely life-like tonality, good midrange presence, very tight & punchy and strong bass that remains well textured, both very detailed and natural sounding despite the big bump in bass (versus much expensier headphones mostly lacking airiness and soundstaging which are Q40's weaknesses).
With the last setup it handles everything from bassy EDM music to female vocal performances like Celine Dion or whatever really nicely and while I mostly listen to EDM I also listen to calm, relaxing ballads, some pop, some rock and occasionally orchestra (game music), even some newgen jazz & rap xD. The bass on my setup never gets in the way when listening to music where the bass shouldn't be in the focus, when I listen to female vocal focused music, they sound like being in the focus, when listening to bass-driven EDM music, the bass is in the focus etc, just like I want it to be like.
So yea my setup is the last one...
Edited by RPGWiZaRD - 11/18/13 at 12:02pm