ADK A-51
I've got a couple of the ADK A-51's. They're OK for what I paid for them ($200 for a sequential pair off of eBay). It looks like you can pick them up for about $150-175 new retail. For $200, I'm considering ordering a C1 just to see if the hype is justified.
What I've seen of the A-51:
1) Deep male vocals sound good when you take advantage of the proximity effect-very full, very rich.
2) I've used a pair of them in stereo micing a variety of acoustic guitars. I had one about 8" from the soundhole, and one about 8" off the neck at about the 14th fret. Very nice, detailed sound. A little lacking in low end, but that may be a function of the guitars used and the room (my room sucks).
3) The supplied shock mounts and mic clips look good, but are a pain in the rear to adjust.
4) I haven't done any female vocals with them yet, but will probably get some done this week. I'll update the post if I hear anything worth posting.
Without having a V67 or a C1 to listen to in the same room, I can't give my opinions of those mics. However, I'm not unhappy with the sound quality of the ADK's I have.