IMO, using STX -> Burson -> HD600 was good enough. I will just present the thoughts that ran through my head. Whether I continue to have the same opinion even a week later is up in the air
- Full size cans go with full size headphone amps
- A well rounded sound stage
- I do not have to feel that I sank big money down the drain for the Burson
1) I had the audacity to use the Thunderpants with Clip+ and did not find anything to be a hugely better setup back then. With HD600, the portable gear I used (QA350 -> UHA-6S) is much better than Clip+ and is not short of power to drive the HD600 to loud volumes. Yet, with STX -> Burson combo, I felt that it's futile to use portable amplifier with full size cans. It's not the loudness per se, but Burson had better control and refinement in the end.
2) I am not much of a sound stage size freak though I'll be the first to admit that I have a certain weakness for large sound stage. More than the sound stage, it's the presentation which matters. EX-1000 always gives me a large rounded concert hall feel where I am at the center and hearing from performers all around me. HD600's presentation was slightly more rounded and filled with the Burson - I could easily locate an image at a certain place defined by all three dimensions rather than just length and width. Sound stage is not exactly QA350's strength as it lacks depth. UHA-6S improves on this aspect while retaining clarity, reducing a bit of that brightness and in general, add some cleanliness to the sound. However, with Burson, HD600 had a better feel. I would not even describe it as warmth.
3) So far, I was very underwhelmed using Burson with MS1i as I expected a huge jump in SQ, which was not present. Sometimes when you reach a stage where the game is not so much about glaring defects (which is the least defective) and everything is pretty much level on a good basic SQ (which is better
preferred), it's the smaller things which decide the matter in favor of one thing or another. Head-fi has a tendency to blow these things out of proportion and show off a 2% difference like it means the world in the end. I thought I had succumbed to head-fi curse yet again. I thought I will figure out what the f#$% PRaT is the moment I start using the Burson (no offense to Mike @ Headfonia), but no matter how hard I tried, I still don't "get" it. I was in fact a little underwhelmed when using MS1i with the lower impedance output jack. But, with HD600 in the high impedance jack, I felt happy. I even considered getting another headphone, but my wallet is not where my mind is, so that was skipped.
This "feeling" has nothing to do with objective proper A:B comparison though
PS: Burson has an output impedance of 5 ohms for the headphone out, which might not work well with IEMs below 40 ohms impedance. On top of that, SM3 is notorious for not liking amplification much.