I haven't heard of anyone running km185's, but even the km150's are pretty rare for tapers. I ran km150's for awhile, though I preferred my km140s.
I'd guess the km185s are very, very similar to the km150s, but still both are pretty rolled off in the low end and may not be the best suited for full-frequency music recording (unless you've got so much low end that you wanted some rolled off anyway).
The km185's are about 16 db down from flat at 30hz, which is about 8db lower response at that frequency than the km140s, and 16db lower response than their very flat omnis. And probably 6db or worse in low end response than the mk41's.
I found the km150s to be good for small, crappy sounding clubs where you wanted hypers to deal with the poor room sound, but were close enough to the subwoofers that a good amount of low end rolloff worked to your advantage. But the km150s for me weren't good for b-ball arenas or whatnot where you wanted hypers since you were so far back. In those instances, there just wasn't a lot of low end response on the tapes.
As to used, I've only seen km185s come up very, very rarely on ebay, never on ts.com.
Of course, I'd recommend the Gefell m210's over the km150s/km185's and over the mk41's, though I don't know how they compare on price. For lower cost hypers, I'd def recommend the AKG 483s. I ran those for years and liked them far better for what we do than the km150's.