Wow, I'm glad I got mine when I did.
I used the HS2 for several hours to determine there was no benefit to keeping a recently purchased (refurbished) HiFiMan HM-801 as a card reader to Line Out vs. sticking with my 3-year-old Sony PCM-M10 (which has a very nice 24/96-capable, proprietary sigma-delta DAC). Had I been interested in using the HM-801's headphone amp, there would have been no contest. The PCM-M10 headphone amp isn't even as good as a Sanza Clip+. But for my purpose of wanting only a card reader and a DAC to Line Out, the PCM-M10 has won a very close contest.
The HS-2 made this comparison very easy. It's an awesome tool. Thanks James!!
I returned the HM-801 today, under their very generous 30-day refund policy.
Results of my comparison can be found here: http://www.head-fi.org/t/456327/sony-pcm-m10-as-portable-player/165#post_9799784
By the way, I would love to see FiiO make a portable device that's nothing more than an SD card reader with a UI similar to the X3, with a killer DAC to analog Line Out (for use with both desktop and portable amps), supporting at least FLAC to at least 96/24. It would have no internal amplifier, nor any other bells and whistles. I should think this could offer (hoped for) X5 sound quality at an X3 price - thanks to fewer parts.
To my knowledge, no one is making such a product and yet, there are so many portable amps to choose from, with so few portable sources. Everybody's buying DAPs with amps, then connecting them to more powerful external amps. It doesn't make sense having to buy parts that get left out of the chain.
Mike