These ratios are really good starting point.  Even with my under $1k budget setup, the numbers are really close to what I have invested or will invest.
Waiting for that one new unmentionable dac upgrade from the nordic guys.

Where I am having a hard time with it is in the under $500 area where each half go to amp and cans.  Assuming tablet, laptop or phone as source, I think one might get better results by using some of the ubiquitous dac/amp combos.  I know whenever I used one of the 3 sources above, going analog out and dumping it into an amp did not work nearly as well for me as using something like a Microstreamer.

All in all, though well thought out and good points in the follow ups.

Continuous pot just makes everything sound good good, especially to the idiots performing it*. 
 
But seriously... people aren't aware of that cheapest of hifi upgrades? The volume knob? And how changes which are too small to be perceived as changes of volume can appear to be changes of sound quality?

Anyone who isn't is not getting the best of their volume knob. Or is just not thinking about how that merest touch can change discomfort or dissatisfaction into delight without making the music actual feel more, or less, loud

And the only piece of audio theory that most hifi salesman ever learn: Louder, if not already too loud, is always better... "Try this amplifer, sir, I think you'll find its tones deeper and rounder and altogether more...Aaagh! Don't touch that knob!"

Thus the need for level matching in any serious testing.

But, as for the practicality of all that stuff, including blind testing of hardware, don't ask me! It is too much like hard work. Accordingly, I don't claim to have ever done any really serious testing --- including of the stuff that I buy or don't buy.


(*Yes, I'm still a committed Grateful Dead lover. No, I don't have any problems at all with psychedelics, although I left them behind 40 years ago. But I remember how clever we thought we were, doing the stupidest things. Hey ho, it was fun at the time) 

I've started to look at it this way:
Buy class A stereoamp.
Buy Yggdrasil or any other R2R DAC
Then buy whatever headphone you want.

I'm amazed by what a class A amp like First Watt F6 can do, even with LCD-3F.
My Mjolnir is literally garbage compared.

I've been thinking of using stereo amps too for high impedance headphones since they need a lot of gain anyway. The First Watt F4 seems damn near ideal for headphone use since it has a gain of zero.

Do you have any problem with noise though?

I've been thinking of using stereo amps too for high impedance headphones since they need a lot of gain anyway. The First Watt F4 seems damn near ideal for headphone use since it has a gain of zero.

Do you have any problem with noise though?

Yes, you won't want to do that with a sensitive headphone with the HD800. I have a First Watt J2 and have tried my HD800, LCD3F, and HE6 through it.

The HE6 is insensitive enough that there isn't any noise, but the HD800 and LCD3F have background buzzing with the amp. I've tried various isolation solutions with no luck. The buzzing is quieter on the LCD3F, and isn't really noticeable once the volume's turned up.

The First Watt works great with the HE6 and maybe other similar orthos will work, but I probably wouldn't recommend any dynamic headphones to pair with it. The HD800s sound okay with it but something like the Balancing Act will be much more satisfying. Orthos work pretty well with speaker amps.