The consensus on re/blue vs. gold is mixed. Most opinions I have heard favor the red/blue 105W for sound and ability to drive low impedance loads. Most opinions hold them as only subtly different sounding.
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1074209541&read&keyw&zzst-140+red+blue
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1163363785
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1201935167&read&keyw&zzst-140+red+blue
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1074209541&read&keyw&zzst-140+red+blue
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1163363785
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1201935167&read&keyw&zzst-140+red+blue