Regarding the Stepdance vs. PB2...
I still use the original Meier Stepdance (not the 2Stepdance or the newer offerings) and I drive it with external 15V battery packs (to maximize its output power to the headphones). I use the Stepdance in my "walkabout rig" - where I want to keep the weight and size of everything to a minimum with this chain: Sony PCM-M10 -> 15V Stepdance -> headphones
I love the sound of the 15V Stepdance so much, that I bought another Stepdance, just to keep on hand as a spare, in case the first one dies or gets damaged / stolen / whatever. I really like the Meier Stepdance and consider it to be far more sophisticated a design than the iBasso PB2.
Where the Stepdance is sophisticated and sounds great, the iBasso is somewhat crude, but can be upgraded to sound even BETTER than the Stepdance WHEN you are using power hungry headphones like the Sennheiser HD650, the Audeze LCD-2 or LCD-3, or especially the HiFiMan HE-6.
With a 16-Volt external battery pack (not the internal, 12.6-Volt battery) and the use of balanced output to your headphones, the iBasso PB2 is far more powerful than the 15-Volt Stepdance (up to 2500 mW vs. perhaps 900 mW).
After upgrading the PB2 with the "right" op-amps (which, in my opinion, are the LME49990's and HA5002 buffers), and buying balanced headphone cables (which, in my case, are the Silver Poison by Toxic Cables), the iBasso PB2 definitely SOUNDS BETTER than the 15V Stepdance, into the LCD-2.
It's a matter of MORE POWER plus BALANCED OUTPUT winning the day, with the LCD-2 really coming to life when given sufficient power.
When using IEMs or far more efficient headphones than the LCD-2 (like my Shure SE530, Sennheiser HD280 Pro, or Philips CitiScape Downtown), the 15V Stepdance has no problem competing with the iBasso PB2. In fact, I would give the Stepdance the edge in terms of sheer transparency, neutrality, and resolution.
But overall, I'm willing to suffer a slight reduction in resolution and transparency, as well as suffer the PB2's noisy, archaic, analog volume control, to get the awesome dynamic range, bass extension, and bass control (detail), that comes with running the iBasso PB2 with a 16-Volt regulated external battery pack, LME49990 op-amps, HA5002 buffers, and balanced output to the LCD-2, via Toxic Cable Silver Poisons.
Replace the LCD-2 with efficient headphones, and I'm back to using the Stepdance instead of the PB2.
My interest in USB DACs is strictly for desktop use, where I would always be using the LCD-2, and thus, the 16V iBasso PB2.
Regarding your forthcoming comparisons of the Triad L3 and ALO RX Mk-3...
Will you be using balanced output with either of them? I suspect that singled-ended into power-hungry headphones, they wouldn't be able to compete with the balanced-output,16V-powered iBasso PB2 - but I'm just guessing.
I'm really looking forward to your impressions. Will you please send me a PM when you've posted your findings?