You definitely got that from the SR-60 mod thread. I've seen the drivers, they're pretty much the same construction and spec. The cable is what changes and the venting of the diaphragms is what gives it that better low end. That cable is rather expensive to product on their end by the way since it's all done in-house.
See, I've read somewhere on these forums (not sure which post) that all of the drivers from the low end all the way up to the high end are actually really similar. I'm not sure if this is entirely true or not, and you're saying it's not. In the event that they are pretty similar, then the housing and cabling are the biggest changes, which aren't too expensive to upgrade. And I'm thinking the only reason I would do a recable is that the stock cable annoys me with how it gets tangled all the time and I want to be able to disconnect my cable right at the headphones (I'm thinking about going with a mono jack in each earpiece).
I love Grado. Nothing like listening to scorching hot lead guitar with the volume up and clenching your teeth from how good the treble sounds (to me at least). Also I find that Grados sound better at lower volumes than most cans because since they're so bright, you get a lot more detail at lower volumes. My Senns are more comfortable to listen at moderate levels because of the neutrality though.
My heart jumped for joy when i saw the Grado article on the front page by the way. I had no idea they'll still service all your headphones past warranty! It really helps that they've more or less been making the same headphone for close to 20 years so they'll always have parts on hand!