Yes, in theory they should all sound the same. In practice, that's not always the case. Some devices, notably some of the Edirol products, upsample all audio to 48 kHz before outputting the digital signal. You want to avoid this at all costs. I know the Sonica doesn't do this, and the Sharp is fairly new so it probably also doesn't (but I can't say for sure). Also, different devices can have different amounts of jitter. The effect of jitter on the sound is debated, and depends heavily on associated components, but I think I can detect a difference in the quality of the digital outs between my Delta DI/O 24/96 and my Sonica, but the difference is minor. As long as you get a decent device I wouldn't worry about it.