I've listened to them on a number of occasions (I live in Japan and every high-end store seems to have a pair at some time or another). The K2 9800s are nice - they are much more musical and 'complete' than the standard JBL monitors and home audio speakers (the S2000, etc) and are definitely a step above the K2 5800s. That said, I could definitely find better ways to spend that kind of money (or even quite a bit less) on speakers. I find them a bit colored in the range of cello music and despite their sensitivity, orchestral music can be a bit muddled without a decent amount of really good-quality power (especially in the mid-range). They do female vocals really well.
FWIW, they usually go for abt $13-16k used in Japan.
FWIW, they usually go for abt $13-16k used in Japan.