The Audio-technicas are a good choice, but based on your zeal for bass, I highly recommend the Beyerdynamic DT770 Pros. Built quite ruggedly for great durability, they have fantastic, thunderous bass response unlike anything else I've heard in the <$200. IMO, they are much better than the Sony XBs as well since the Beyers do not sacrifice as much mids. Plus, they are über-comfortable; their velour pads are like pillows.
I've always enjoyed my pair of DT770s before selling them to get the Denon D2Ks. While the Denon's bass is arguably best <$350, there are just some days I still miss my DT770s.
I currently own a M50 and they aren't a bad choice. But compared to the DT770s, they have significantly less bass response and are about a trillion percent less comfortable.
If you're interested, be aware there are several models out there. 3 models are based on impedance: 32, 80, and 250. I had the 80 ohm version. I wouldn't buy the 250s unless I had an amp. 32 ohm models are the easiest to drive off an iPod, but they are rare and a tad expensive (found over $200).
Hope this helps!
Edited by Empire1 - 10/14/12 at 9:03am