The standard operating procedure seems to be is that he either emails you and then sends a google invoice or just sends the goodgle invoice. Either way, you should know when he wants you to pay and then get your amp shortly thereafter.
Who knows, haven't really seen that much activity for Ultrasones, although I guess the new one has restarted the craze. RSA amps are still king of the long burn in, in my book.
Can't say I've ever really screwed wit hte Ultrasones, although from all reports I'm not missing anything good. The GS1k when I heard it, was awful however. So what's your rig then?