From: Yahama Corporation of America

The Yamaha RBXJM2 John Myung signature six string bass is now available. The model supercedes the existing RBXJM six string.

http://www.giles.com/yamaha1/pr/mus/guitar/2004/RBX_0404.html

In other Dream Theater related news, Dream Theater have announced that they will be releasing an upcoming live CD / DVD from a show in Japan.

The advantage of the DVD format is that even though you can't hear John Myung, you can at least show your friends that Dream Theater do have a bass player. :D

http://www.dreamtheater.net/news_dreamtheater.php#dvdjapan