Audio Technica ATH-M50 have their fans, but I believe currently their price is a little on the high side for what they offer.
The ATH-M50s were cheaper earlier in the beginning of the year.
How about the Audio Technica ATH-A900s or Denon AH-D2000 (good bass), both are easy to drive.
Also Audio Technica have come out with new closed headphones, the A500X, A700X and A900X.
I'm a fan of the Beyer DT770 Pros, but you need a good headphone amplifier to bring out their best.
If you buy used headphones from a private seller in the USA, might get them shipped into Canada with out any import duties.