Ahdat---
I have all 3 phones and each sees at least a few hours of play per week! Wouldn't want em to feel neglected....
Soundstage: V6 is the smallest. 497 and 280 are fairly similar to each other, much more expansive than the V6. The 497 would ordinarily be expected to have the biggest soundstage, but I think the careful design of the 280 and the cheaper price point of the 497 cancel out the expected advantage and produce a fairly similar sound stage from each.
Bass: 280 is king, lower extension than the V6, which is remarkable. 280 also does better on sustained deep bass and conveys a better articulation even at very low freqs. The 280 for instance is probably the best headphone for tracking bass guitar playing in detail and also sounds excellent with electronica. The bass on the V6 is exceptional compared to most headphones, but is trumped by the 280 for the reasons stated. Finally, the 497 has the least bass of the three, but is still more than fine for an inexpensive open design, and is much superior to the SR60 for instance.
I think Blr is correct---midrange on the 280 is better done than on V6, and this contributes to the overall "musicality" perception especially with vocals and acoustic sounds, which are big stumbling blocks for the V6.
Ahdat. if you like the V6 more as you listen to it, you might want to get the 497s as this will give you two phones with different sonic profiles. Buying the 280s will cost you say $80-100, and then you'll pretty much not want to listen to the V6 anymore, so you'll have spent roughly $150 and gotten one pair of usable phones. If you get the 497s, you'll spend say $120 and have two phones that can be used for different purposes. If you only wanted one set of phones out of the 3, I'd say get the 280s, but with the V6s already bought and not that hateful to you, I say getting the 497s makes more sense.