Awesome thank you for the insight! I wasn't too sure how the Jazz would fair with a planar headphone. I myself have electro stat. speakers in my living room so it actually sounds like our sonic "tastes" might align a little. I am also not that surprised to hear that the Classic is so close to the Jazz, the Jazz is pretty much colorless to me, the proverbial "straight wire with gain".
I communicate with Jan from time to time, and after I had the Jazz for about a year I told him that I really didn't even feel a need to upgrade, I just wanted to make sure I had enough on tap for harder to drive phones for when I added to my collection. He explained that he wasn't surprised how much I liked it, because he considers it one of the best amps he's ever built, but since he typically doesn't advertise and relies mainly on word of mouth and forum activity, it never really took off like he thought it would. He's very conscious about keeping costs as low as possible for his consumers, so I'm always glad to see others who appreciate this great little amp.
And I agree, I detect no coloration or bias with either the Jazz or Classic. I bought the Classic and the Daccord together, but I could have been just as happy with the Daccord and keeping the Jazz in play since the Daccord has the full crossfeed circuit. It drove the LCD2s just fine, and it does great with the Xs, as well. That's the main reason I have not sold the Jazz even though I had some inquires. It's so inexpensive that it's not worth it...it's way too good to sell. For those of us who want a neutral amp, it's a huge bargain, as you know.
I wouldn't hesitate at all to pair an Audeze phone with the Jazz...sounds great to me!