The benefit of the built-in DACs on the Theta is a matter of opinion in terms of the benefits delivered. Obviously, the better the quality of your CDP, the less benefit the built-in DACs will deliver. However, if one has a mid level CDP or already just has a transport, then the built-in DACs can be a real benefit. This is all based on 2-channel listening. Having them can increase flexibility, no doubt (adding digital sources with either no internal DAC or a poorer internal DAC) or possibly doing away with CDP's in favor of straight transports (nice if one already has a 2-piece transport/DAC and they find that the DACs in the Theta are as good as their existing stand alone DAC???).
Pre/pro don't have HT passthrough in the sense that a 2-channel preamp does. What I believe stick is refering to is either a full analog bypass that allows the 2-channel signal to pass through the pre/pro without any processing (outside of gain in the analog domain) for the cleanest/least compromised affect on the signal.
Typically, HT passthrough refers to a feature on a 2-channel preamp that allows the prepro to deliver its front left and right output signal (that would typically go to the associated amps) for a movie (for example) to pass through the 2-channel preamp without requiring the user to adjust the volume from the preamp, but performing all volume control via that of the pre/pro. This allows one to connect their higher quality 2-channel analog signals directly to the 2-channel preamp, leaving the pre/pro completely out of the 2-channel chain for optimal performance. In essense, this allows one to maximize performance for 2-channel and also for surround sound all in the same system!
