Agree with
dalethorn about the V-Moda M-80 as far as reviews for your bass needs and they do indeed look well built and pretty as hell! The only thing is you asked for £200+ and they are only £140.
Since you said no real upper limit I must give you my impressions of the Denon AH-D7000. I got them for £540 from 'Andvanced MP3 Players' yesterday. They have really amazing and insane bass! They are also closed backed, although not as much as some, they are somewhere in between open and closed in my opinion. I haven't had em long but enough to get ecstatic about them and write a small review... ah what the hell I will paste it in here...
Before I bought the Denon AH-D7000 my previous (owned) headphones were: Sennheiser HD565 (£150), HD25-1 II (£140) & Grado SR80i (£120). None of those were really in the same league as the Denon so I was expecting a big improvement, boy did I get one!
Instantly the most noticeable aspects of the Denon's are their powerful bass and the lack of fatigue from highs & high volume. The latter was rather surreal (compared to the above). There is much more power to music with these phones across the board, it makes music so exciting that it encourages you to push volume higher which I know can be dangerous but damn it's a lot of fun! The detail and clarity while rattling your head to bits with bass is really something to behold! Listening to: 'Drake-Still Fly' by Butch Clancy... Wow! *huge smile*.
Also noteworthy for headphones in this range is their ability to be driven from almost any source (volume wise), although I know this can be subjective. I am running the D7000's from my Samsung Galaxy S as I write this and it's pretty good! OK it's at maximum volume but it is loud and although I do wish I could push it higher it's only because of the lovely sound and not because I should. I also tried them with an iPhone (4) and a Cowon S9. Both provide a bit more headroom in the volume. The latter is noteworthy for it's supreme SQ (sound quality), the best from any un-amp'd portable in my opinion, Sony's are close though.
I should mention that although you can power the Denon's from almost anything you probably shouldn't. My main setup has them connected to a Fiio E7+E9 combo DAC/Amp (through a PC) and although it is ok I do get the impression something a bit more refined could push them in a better direction. Maybe one day I will pair them with something like a Burson HA-160DS which matches the Denon AH-D7000's price and according to Head-Fi'ers compliments the sonics too. If I do manage this I will update this review with my findings.
The characteristics of these headphones suit a variety of music. My favourite genres are: Soundtracks, Metal, Industrial, Rock, Classical, Electronic, Pop, Jazz etc. The Denon's have given me a massive boost for almost everything! It makes bass heavy music hit with such impact it's difficult to go back to anything else! Anything orchestral gets so much more weight on the low end without too much colouration that it has made most of my collection feel much more dynamic and engaging. Jazz is great for the same reason. Perhaps vocals (mids) get the least attention at this price point but that's not a huge complaint. They sound a little resessed so that they can that fun 'V' shaped response from the lows and highs. Perhaps if you consider the sound characteristics (glass shattering highs) from Grados to be perfect you may not like these headphones for their slightly non-linear response. However I do not want to suggest that the D7000's are all about bass, far from it. For me the D7000's are about fun, powerful sounds with a great deal of detail and control. The bass is lovable but not overcooked, it has texture and depth that you will not hear on lower end fun phones.
I should probably point out that although the D7000s are closed they're not very well closed, if you are looking for high performance in the isolation department you will be disapointed here. When you are enjoying music (loud listening) people next to you will hear that you're listening to something, they may even hear what you're listening to if your surroundings are quiet. Compared to an open pair of headphones there is a big difference but there are much better closed phones out there too, just not with this level of performance (possibly the Ultrasone Edition 8's?). There is a clear comprimise being made here.
Comfort?... yes! They are really comfy, for long periods too. They do not feel heavy and they clamp my head just hard enough to ensure they don't fall off to easily. For me (and this will be subjective) they are perfect!
Build quality is lovely and the wood / Aluminium makes it look and feel the asking price! Not quite my style I must say but they're not horrible. The headband and cups are real leather (although some say they are not, perhaps because they look the same as the AH-D5000 which are pleather). The cups also rotate to help get the best fit and isolation, this is a nice touch and it does indeed help!
If you are considering the Denon's but are concerned that headphones of this price should not be so much about bass... Firstly I highly recommend trying them out (from a good source and amp if you can), if that convinces you something more neutral is for you I would I suggest checking out some of these:
' Audeze LCD-2
' BeyerDynamic Tesla T1
' Ultrasone Edition 8
' Sennheiser HD800
' Hifiman HE-6
Be warned: The price shoots up from here and from what I have read you'll want to be pairing these with a similarly priced DAC/Amp to get the most out of them. Most of these are not as forgiving as the Denon's for volume but also for source quality and also amp pairing.
You could say that I settled for the Denon AH-D7000s looking at that list but I am not regretting my decision one bit, I really love the sound characteristics that these phones offer. Although I reserve the right to be tempted by others in the future I see the improvements heavily encroaching on the laws of diminishing returns at that point.
I read a lot before getting these, if you want a lot more info on these and what they compare to I highly recommend checking out the Head-Fi forums.