Thoughts on Sonarworks
There is no question that the EQ curve that Sonarworks gives HD800 is the single most significant sonic change possible to the headphones: more so than DAC, amp, and indeed the physical mods to tame the 6khz peak. It is uniquely able to be turned on and off instantaneously. While the EQ'd sound is essentially a prerequisite for every genre other than classical, I am oddly indifferent about its effect on classical music. Although Sonarworks improves listenability of poorly recorded and 'historical' recordings, the stock treble energy creates some of the sparkle that adds a secret sauce to many well-recorded documents that I am loath to give up. The EQ unquestionably reduced the soundstage. Furthermore, while few would call HD800 a "euphonic" headphone, I find its stock colorations (albeit entirely on the bright/cold side of the ledger) to add a naturalness or realism to some classical music that the more neutral frequency doesn't provide. The sense of space feels more well-defined, even as the sound is less emotive and satisfying.
Perhaps this is an instance of masochistically finding something worthwhile in what is not strictly beautiful, of coding harshness or abrasiveness as "accuracy," but for orchestral music (and nineteenth century orchestral music more or less alone), I think I will use SW perhaps half the time, and bypass it the other half. For piano, chamber, and pop, stock is more or less categorically inferior.
Sonarworks is uniquely adept at eliminating white noise. For instance, in the Kempff stereo Beethoven cycle, although SW leaves in some low hiss in the middle register, the treble cut reduces the sound dramatically. Moreover, that lower register is less noticeable by far than the treble.
SW is cheaper than a tube amp, cheaper than a multibit dac, cheaper than going balanced—it's 5 months of Tidal, to the dollar, and I would take a 256 kbps source though SW over lossless without any day. We should create a flowchart for chain recommendations for HD800.
Are you using SonarWorks? Yes -> Your Magni/Modi stack is probably fine, though Vali/Mimby may give you that last 10-15%.
No -> get SW, or get MJ2, Gumby, balanced cables, '75 Reflektor tubes, and still find HD800 just "ok" for anything other than classical.