...Sennheiser PMX60s.

Cord went on the portable headphones for my MP3 player this morning, and it is essential that I have another pair soon. Since I get so much use out of these headphones, I'm willing to spend up to 100$ CAD.

Could any of you super-technical savvy headphone people recommend some great headphones designed for mobility?

They've gotta have...
-decent sound quality
-not use too much power (an issue with volume and battery drain, my big cans don't go very loud because they don't get enough juice)
- be small and light, easily portable. PMX60s were fantastic in this department - very comfortable for walking, running, hand around neck while not in use, extremely light.
-durability, I'd like these things to last. I don't want a pair where the cord is gonna give every 2 weeks, they should be able to stand up to a minor beating. I'm not willing to resolder them every week only for them to break in the next few days.

Senn PX-100's or 200's.

Ultra-win.

I agree, the PMX60 aren't great anyway. PXC 250 if you want active noise cancelling. They're like the Bose QuietComfort 2, except they sound a whole lot better and isolate a whole lot better without the Bose marketing department price tag.

I would also suggest the Shure E2c if you want some nice isolating canalphones. Canalphones are like earbuds except they go way into your ear canal, much like earplugs, so they isolate a lot of sound. They typically sound uncalculably better.

Also check out the Koss KSC75. They may well have the best sound out of all of these, depending on your tastes. Don't be fooled by them being clip ons - just spend about five minutes on Head-Fi and you'll find a lot of audiophiles raging about these. Many consider them to be some of the best sub 100 USD cans, period. They may not be as detailed or as exact as more expensive headphones in this range, but they have a warm and fun sound do them, which apparently appeals to many. For about 23 (28ish CAD) shipped online, it's probably the best headphone value there is. They have this cool, almost retro 1950's alien saucer look and some comfortable rubber covered wire clips. They use the same drivers as the KSC35, but are more comfortable and actually retail for $10 less (my guess is no need to pay for R&D).

Everything I've mentioned should be driven well by most all portable players.

You might try searching Head-Fi for more details and reviews on all the cans mentioned.