I made the pre-order and surprisingly got it just an hour ago.
About the amp section, the first thing I can say is it's really powerful and it has more bass than the Protector, paring with all 3 pair of headphones. The Intruder produces really smooth and warm sound. For first impression, I listened Kitaro's
"Matsuri", A. Bocelli's
"Vivo Per Lei", paring the Intruder with the HD600s, HE-400s, and Westone 4s.
I cannot hear any difference yet between the single-ended and balanced outs with my HD600, except the volume. I got a decent volume with my beloved HD600s using the balanced out, even at the lowest gain. Probably I need better ears or better headphones, then
However, I really like this combo. Finally I can have some decent bass from my HD600s and I think the Intruder will be my main amp now.
When I paired it with the Hifiman HE-400s (2nd rev. btw), single-line out, the combo is a bit darker than my taste and I like the combo D12+HE400s better.
Finally, I have to admit that I've never heard my Westone 4s sound that good. The Intruder+Westone 4s combo synergy is just awesome. It has the strong bass effect of the Intruder and still maintains the clean mids and highs of the W4s. No hiss at all, of course.