Worth it though...unless you are on a budget of course then buy these
For me noise cancellation is also not a big deal so the increase in cost would not be worth it me. From what I have heard, the xb900 is the right choice if bass is your thing however as an overall package the MX3/MX4 you cannot go wrong if you want to stretch.
I haven't tried the Xm3s but are they just lacking bass and gaining on the noise cancelling and is that worth the price difference? Got these xb900n's yesterday and was blow away by the sound quality, but then noise cancelling isn't a big deal for me, headphones for music an all that...
The 1000MX3/4 are apparently really good for that although double or more this price.
Pristine Xm3s for £139 probably more appropriate