Glass Fiber AT&T ST or AES/EBU XLR ?

I can't speak to the Theta but I can tell you that I went to 2 Aural Symphonics Optimism v2 cables between a 270SE and 27. The clock signal cable was a real improvement. The music signal, IMO, has become extremely clean and analytical. I would call it incisive, not harsh just extremely detailed. For my taste, maybe a little too detailed. I am considering a new cable (XLR) with a touch more warmth. The problem is that there are so many digital cables available that it's mind boggling. JMO here but if I were you I would stick to XLR but maybe try a few others rather than pay to upgrade the Theta. You could purchase a great XLR cable for the cost of a Optimism v2 and the Theta upgrade.

Mejames,
Are you saying the Wadia will lose clocklink with XLR? I was under the impression that clocklink will work with other connections. Am I wrong here? Of course I will leave the AT&T between the units for the clock signal. Maybe I need to go back and re-read the manuals.

Mejames,
Just received an e-mail from Keith at Wadia. The clocklink works with any cable. Of course the clocklink must be connected by the AT&T glass cable and transport and DAC have to be configured for clocklink. As long as this is connected and active all other cables no matter which termination will carry only the word data. This is as I suspected but I was not positive. Thus the confirmation from Wadia.