Okay, I now see what the fuss was about. My problem was insufficient power. These 627s are power hungry. They eat pairs of 9 volts like candy, but they are surprisingly revealing. I still laught at the bad rap given to the 823 but now, in the shadow of the 627s, they seem less spacious - sort of like comparing the SR60s to the RS1000s or the GS1000s.
I'm hearing details I'd never heard before, and I'm hearing them on tracks I'd never expected to "rediscover." I'm hearing more dimensionality to the acoustic twang on "Yesterday," and there's a creak - like a door opening - around 18 seconds in. (What the Hell was that?) On "Someone Saved My Life Tonight," I discovered that cross-channel flutter/echo of the electric piano. (Before, I'd always heard the piano, but not the flutter.) I don't know why I'd never heard the electrical whine, fore and aft, on Cake's "Italian Leather Sofa." Even the Carpenters are hiding a breath in the right driver, about ten seconds into "Top of the World." Men at Work's "Overkill" is still gratingly sibbilant while Billy Joel's "Half a Mile Away" has a weird hidden chirp one second in and you can hear BJ say something under the music about eight seconds later. Bob Marley's "I Shot the Sheriff" sounds more live. Keyshia Cole's "I Remember" sounds pluckier, and with a thumping bass. Weezer sounds about the same but on the Beatles' "A Hard Day's Night," Ringo's "Wipeout"-like drumming is more prominent, as is the shredding of somebody's rhythm guitar. When somebody near the stage (ironically) coughs through the opening of George Carlin's "Autoerotic Asphyxia," it's no less a find than the extra texture on The Cars' "Bye Bye Love."
Yes, these 627s are keepers, though - when size and voltage matter - I'm happy with the 823. I have two Cmoys, so I'll probably keep the 823 in one unit and use the 627s in the other. I just love that instrument separation. I could get used to this.