$400 seems high to me. I've got an M500.....used it for a while, it never blw my socks off, then I blew the ribbon. I sent it out to Stephen Sank and he did his DX mod on it (replaces the ribbon with an RCA 77 stock ribbon). The mic is much better now, its a little on the bright side as it's meant to be a close talker mic, but its pretty cool. I'm interested in trying it on snare....hope the ribbon holds up!
Don't be fooled by the hype though, even with the DX mod, the M500 doesn't sound like my RCA 77D (also refurbed by Mr. Sank). A ribbon element is just a small component of the mics sound, there's the transformer, the grille, the acoustic labyrinth, the motor (magnet)...it all adds up.
My recommendation, find a blown M500 and send it to Mr. Sank. For less than $400 you'll end up with a nice ribbon mic that'll be quite different from your M160.