I need a set of closed headphones for DJing. Right now I have some AD700s, and although they sound great they aren't closed. They also have a ugly headband, I need to find some way to replace that.
 
Anyway, my main concern is isolation. It'd also be nice if they were comfortable, and of course they have to sound good. I'm really worried about comfort, right now I wear my AD700s all day and I know there is no way any closed headphone with any decent amount of isolation is going to come close. Here is the list I have right now:
 
HD 25-II - Seems a very popular DJ headphone, I'm a bit worried about comfort though.
 
SRH 840 - Heard a lot about them here, but isolation seems to be one of it's weak points
 
ATH M50 - Not sure about the strong/weak points on these
 
HD 280 - I've heard these once before, tons of isolation but dull sound. Also lots of clamp. 
 
The absolute price limit is 150$ USD. They will be used with either a NI audio 2 DJ, or a cowon X5L. 

Of those HD 25 II should have the best isolation.  BTW these are a lot bigger than they look in pictures.  Should cover your ears and create a very nice seal.

Senns are default choice if your budget allows this amazing 'phone. Due to unbelievable good isolation they can be a bit uncomfortable but you can add velour pads which will help.
You dont have to worrie about their size they are smallest can on your list. Ultrasone dj1 pro is another choice , they are over the ear.

The HD-25 is probably one of the best choice and for good reason too.
Bulletproof build, excellent bass impact without drowning your highs (or the mids for that matter) and good isolation, all of what you need for your awesome mix session. It's not supreme comfy (unlike, say... Beyerdynamics DT770), but you wouldn't mind to have it on your head for a long time.
I've only listened a couple of times the HD-25, but that was  enough to convince me that these headphones can help you track the beat properly.
 
However, the sound isolation isn't as good as the HD280, but at least the HD-25 have a better bass "thump".
 
Another good choice is the M50, it has good isolation, but less than the HD280. Not to mention they aren't that comfortable compared to some other headphones.
Mind you, once they are adjusted to your head, they are quite comfortable.
Other than that, it's similar to the HD-25. Probably not as strongly built (the cups don't feel quite as resistant vs. the HD-25) but the M50 has much deeper bass response. On a side note, I've tried mixing with the M50 and they are perfectly fit for the job. Oh... and they are fun sounding too!
 
I'd go for the HD-25 first and the M50 as substitutes.
 
If all else fails, Ultrasone apparently makes pretty good monitors.

I just found out we have a review section. Cool.
 
Between this and the reviews I think I'm gonna go for the HD 25-IIs. I noticed all the reviews and stuff around here say they are 200$, but you can get them from amazon for a little over 150$. 
 
Thanks a bundle guys. 

If you can find them used, the Beyer DT 770M is supposed to have extremely high isolation.

Fingers for HD 25´s too, and for your consideration, you could choose from various types of, you will see-which of them you´ll appreciate most:
 
Quote:

HD 25-1 II - 70 Ohms, 1.5m steel cable with rt.angled 3.5mm mini-jack and screw-on adaptor to 1/4" jack. These come with leatherette *and* velour earpads and a drawstring carry bag.

HD 25-1 II Special Edition - 70 Ohms, 1.5m cable with rt.angled 3.5mm mini-jack and screw-on adaptor to 1/4" jack. These come with only leatherette earpads and a nice zip case. These are no longer available as far as I am aware.

HD 25 II - 70 Ohms, 2m steel cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack.

HD 25-C II - 70 Ohms, 2/3m coiled copper cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack.

HD 25-13 II - 600 Ohms, 3m steel cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack.

HD 25-SP II - Lower quality version without the split headband, 60 Ohms, 3m cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack. (http://forums.dvdoctor.net/showthread.php?t=50863)

Click to expand...

After I own the HD-25ll... I can highly recommend the GMP 8.35 D Monitor.

The isolation on the Shure SRH750 DJ's is pretty good. 

Good choice with the HD25s.