Several people on these forums claim that the Q701's are a bit fuller/warmer sounding than the K701's. I've even read a review which claims the exact same thing. And seeing as there are other changes than purely cosmetical ones on the Q701's(like the foam-piece behind the outer-grill) I do indeed believe that there is a difference.
It should be easy enough to mod the 'k' then, to sound similar, or even identical, to the 'Q', by putting some foam behind the outer grill. It's damn hard to get off though, so I tried tape over it. Also the 'friend or foe' mod (do a forum search if you've never heard of it) can warm them up slightly. But are the drivers identical? FWIR they are, so it may be just some simple mods that are needed. Maybe not so necessary to rush off and sell your 'k' to fund the purchase of a 'Q'. Seems like a there's lot of 'k's for sale on ebay lately.
Edited by lejaz - 2/14/12 at 4:44pm