I'm using JTS HP-525 for good quality noise isolation these days.
Pretty cheap, sound good, go loud without distortion and drummers LOVE them because they are light but have a very tight grip so don't fall off.
It is rumoured that they have the same drivers as Sennheiser HD25.
I have M50s that I use to check mixes but find them to sound very good, almost hi-fi.
My favourite headphones for mix checking are Sony MDR-V55 which are extremely revealing in the tricky low mid area and immediately highlight any problems in the mix.
I would highly recommend the Sonys.
[ame]http://www.amazon.com/JTS-HP-525-Black-DJ-Mixer/dp/B007PQ7NL6[/ame]
[ame]http://www.amazon.com/Sony-MDR-V55-BR-Style-Headphones/dp/B007BY3PNW[/ame]