I've tried just the app on my phone through analog and through bluetooth. I also tried playing through HiBy app with the amp, and switching SXFi mode on and off.
Honestly, I didn't notice any difference between amp and app. But then I'm using headsets that are relatively easy to drive, HD598 and Nura. Switching the SXFi mode on and off definitely makes a bigger difference.
I suspect that people coming from a home theatre setup and live music will love SXFi immediately, while those who are more accustomed to headphones will take a while to warm up. The spatial difference from regular headphone sound is clear as night and day, outside the head vs inside the head. However, I found myself missing the regular headphone sound at first. A good headphone setup creates an intimate mini-theatre in your head, with clear spatial specificity, and super-charged resolution that one might not get even when listening live. Details are amplified, perhaps artificially. But if you've grown to love such an intimate sound signature, then you might feel an initial letdown when first trying SXFi. I found myself asking, is this really the "better" sound? While the sound has been taken out of my head, the spatial specificity - the direction of the sound - actually felt a little poorer. And some details seemed to have lost their "lustre".
I have a nice pair of Elac 330 Crystal Edition, but alas not the right room for it... (SXFi is designed to emulate Elac sound, but of a different model of speakers.) I've been more reliant on my HD598, Nura and Aurvana 3 for the last few years.
Now, having using SXFi for about a month, I've really come to prefer it for most things. It's not so much that the details are lost, but that I had grown accustomed to a different mode in which they're presented, i.e., in your head. Now, SXFi just feels much more natural.
