Old and Curious: The latest beta for the X3 does have play through folder. I personally think that even though it is labeled as beta, that X3 firmware is terrific and shows off the X3 in its fading glory very well.
Castle of Argh: First of all, I must admit that I smell of elderberries. Just had to put that out there. Now, you seem to take on the concept of chipsets having a sound signature. Is that really the stance you meant to take? If all chipsets sound the same, then why do so many enthusiasts think various DAP units sound different Just the firmware or the amp circuit?
well most DAC chips, when ideally implemented by the manufacturer, can pretend to amazing specs like beyond 100db signal fidelity in most measurements. given that almost everybody fails to pass a 16 vs 24bit abx, I would think that 96db is a good point to start talking about transparency. so DACs good enough down to -100db or even below will tend to sound the same too. that's how I see this. simple signal fidelity's logic, as I in effect didn't have the opportunity to test DAC chips alone in a controlled environment. at best I have whole DACs so it tells me nothing about the chipset alone and I don't dare to make theories about one thing in the box when all I can test is the entire box.
none of those making the claims of a difference care to, or can, verify that the differences they hear come specifically from the DAC chip itself. they just take 2 random occurrences (yesterday I saw a black cat and then fell down the stairs, so black cats bring bad luck) and decide they are related. the DACs could have a different sound because of a different impedance, because of a different voltage output, because of the output stage itself being widely different, because of some grounding issue or because of what they ate for lunch for all I know.... but nobody even thinks or cares about those stuff.
then there is the good old bias at work. and once you think "sabre DACs are neutral and cold", the next time you will hear one, how do you get away from that psychological bias? you can't really unless it's a controlled blind test. so most likely it will sound neutral and cold to you. and there you go with the DAC chip urban legend.
can't blame people for having ideas and opinions, but I sure can blame them for making claims they can't support ^_^.
now obviously not all DAC chips are implemented in DAPs the exact way the manufacturer recommended(for money or space reason I would guess). and that would lead to subpar measurements compared to the manufacturer's specs. that may in turn have a special sound. and maybe that's what led to the idea that some chipsets had a house sound. but that's a theory at best, I still think that most DACs are able of transparency whatever the chipset they use, as long as the job is well done.
as for "If all chipsets sound the same, then why do so many enthusiasts think various DAP units sound different", I often answer that there are several thousand reports of UFOs over the world every year. what can we conclude? that UFOs are real, or that many people can believe something and be dead wrong about it?
to go back on topic a little, up until now the latest firmware works like charm for me(and so did the previous ones). it's a great little DAP once the µSD card if well tagged and sorted.