2 years after ordering my Poseidon boards I have completed my Mark III clone! The only hiccup I had was arcing to the screen grids after setting the bias on the first amp I completed. I went back and added screen resistors to both amps. (See this topic - http://diytube.com/phpBB2/viewtopic.php?t=1455) This is a modification I would highly suggest for anyone building Mark III clones. After adding the screen resistors the amps have worked perfectly. Thank you Shannon for the nice Poseidon driver boards and thank you DerekVa for the 12AX7s!
Some pics:
http://diytube.com/phpBB2/album_pic.php?pic_id=55
http://diytube.com/phpBB2/album_pic.php?pic_id=56
http://diytube.com/phpBB2/album_pic.php?pic_id=57