Steve,
I have had the opportunity to demo the Analog with the standard power supply. As you note, Vince is hestitant allowing people to demo the unit without their transport for fear that they are not getting the true capabilities of the DAC as a result of the variability of current "music servers" out there. I did a comparison with my Meitner EMMDAC2X, no slouch by any standards and found the Analogue better, in all aspects with those magical qualities you refer to.
Unfortunately, I made the mistake of then trying the Diamond, which as good as the Analog is, takes one to another level still. Is the difference worth it? Only your pocketbook knows for sure.
One caveat. As you have indicated, Jriver with JPlay equals the quality of the transport. I think you should really look into a dedicated Windows server, such as the superb CAPS and/or CAPS alterntives, either in DIY or already built versions. Obvioulsy the more powerful (Zuma variant) servers would be recommended for JPlay but I think you would get an enhanced experience compared to your Mac and Bootcamp. I was leery about leaving my Mac based players but have yet to find a server that bests the CAPS 3 variants.
While the Analog is "expensive", if one is looking for a computer based solution, IMO, getting the standard power brick, with an included 24/384 USB input for $6,999 is the best relative bargain out there. It easily outperformed my EMMDAC2X, at least in my system and in my opinion. Of course the potential buyer needs to recognize this is a SE solution, includes only one input for the price and doesn't include the $2,999 enhanced power supply. So the price, if one wants three inputs, enhanced power supply and volume control can bring the price close to 13-14K, so buyer beware if these upgrades are necessary for your system.
Lastly, despite claims to the contrary, I tried the VC on both the Analog and Diamond and wound up ordering my Diamond without. I know Vince finds it hard to believe that a preamp can sound better, but IMO, both DACS (like all my other prior DACS) sound better through my Audio Research preamp.
Lastly, the phyiscal appearance of this DAC is gorgeous. I wished their Diamond had taken on this new appearance but in the end it is about the sound.