In case you haven't seen it, here's a thread that addresses the difference between the 390s and the 39, from back in 2002.
http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1020275249&openfrom&1&4#1
http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1020275249&openfrom&1&4#1