I was listening to this excellent streaming Christmas music on the primarily Acappella Radio website:
http://www.singers.com/radio/when a group I had not heard of came on and
BLEW me away with their version of Hark! The Herald Angels Sing (live)
I have never heard acappella bass even close to this accurate. I tried to find it on youtube and Amazon and although there were lots of songs by them, I couldn't find this one. I did however find this from a live concert in Korea in 2005, for all you Count Basie Orchestra lovers...
http://www.youtube.com/watch?v=URpLESNyydE