Wow, very cool guys, thanks for all that! I'll bet that was a heck of a lot of fun. Some damn nice stuff there! I concur with everything you guys have been saying and since it looks like there weren't any HD600's there I can definitely vouch for its pairing with the SXH-1.
I'm at about the 30 hour mark in the burn in process myself and all I have used is the HD600's (Equinox). Source has been my Cal Sigma II tube DAC. This amp is definitely a competitor at and in IMO well beyond it's price range (if not triple it's price). Even at these early stages no less this amp's ability to get out of the way and let a huge amount of information come through is pretty darn amazing and considering the price it's a head scratcher. The SXH-1's transparency is absolutely amazing.
It's driving the 300 ohm HD600's seemingly with relative ease. The HD600's are sounding very alive, snappy and dynamic. The SXH-1 seems to have a nice grip on these cans, something I did not expect to happen at all. I've been throwing classic rock, electronica/ambient, Classical and Jazz at it and it never seems to want to favor one genre over another.
Most importantly, to me at least, the SXH-1 gets the midrange right in spades and the bass and treble regions are exceptional as well. John really summed it up well: the amp sounds more transparent than any amp he's listened to in his limited experience and that there is simply more musical information getting to his ears. The sound is detailed and alive sounding without any fatigue. Ditto, that's about exactly what's happening here as well. Rich, seamless, wildly open window to the music. Just phenominal transparency even at this early stage.
Anyhow, great sounding amp indeed. I don't want to get too ahead of msyelf. So far I'm surprised to say the least, this amp is a killer at this price.