Hi Twitch---
basically what Hamsterball said. The 280s have excellent deep controlled bass while the 80s are a bit too loose to my ears. The Grados are THE noisiest headphones imaginable and also let a lot of external noise in; I've tried my 60s on the subway and they don't work out at all. Also that damned annoying stethoscope cable is too thick and inflexible, and the driver mounts spin like pinwheels, making tangles a frequent hinderance. Finally, the Grados are bulky, don't fold, and are even sorta fragile. You couldn't really wear em round your neck when not listening, and if you put them in a backpack, well, it wouldn't be pretty if something heavy shifted inside and landed on them... Conclusion: Grados (60s, 125s, 325s) are fine at home, but travel badly.
The 280s are big, but fold up as well as lay flat. As Commander said they are bulky and you will look like an air traffic controller with em on, but this is really the same with any mid size set of phones. Also, the 280 is super tough and durable, even making the Sony V6 seem loose and rattly in comparison.
The HD25 is NOT a good substitute in my opinion: it has a wafer thin sound stage, is not really comfy with treble, and is generally overly dry and analytical (even moreso than the V6 I thought...). The 25 is one of Senns older designs that I think is showing it's age. I think the 280 sounds much better. The 25 is small, but there are too many other compromises in exchange for portability/subtlety.
The Senn 212: would someone who owns these damned things PLEASE WRITE A REVIEW?!? Thanks. The 212s are the Loch Ness Monster of headphones...
Hope these thought help! By the way, did you do something nice for the person who stepped on those dreadful HD600s? Helping you get infinitely better sounding phones has to be worth at least a beer or two...