Another shout for bogner here
I got an Uberkab for my powerball. Because it made all the other cabs I've ever heard sound like sloppy, thin, depthless toys.
Granted I havent heard all that many, but were talking 1960A, 5150-whateverthestockcabis, engl V60, mesa slanted V30 loaded and a couple of others.
Never heard, but would really really like to -
Vader cabs.
VHT Big Bottom (or fat bottom, whatever its called)
I'd be really suprised if they're better (for metal) than the bogner, though.