After way too much A/B testing, I decided I like the Atlantis+ better than the stock Orchid. The Orchid has a more open soundstage even stock, but the modded Atlantis is more engaging and romantic.
I started modding an Orchid. So far, that means:
- TDA1541A R1 upgraded to a late production TDA1541A Taiwan chip (1998)
- Tube changed from GE 5670 to 6N26P
- Output caps changed to paper-in-oil K40Y-9
- Fuse swapped to "audio grade" fuse that I had an extra of from the Atlantis+ (I still can't seem to hear fuse differences. Shrug)
I'm not sure if I've changed enough to call it the Orchid+, but I'm calling it that anyway because I'm the one who's typing. It also came stock with most of the cap upgrades that were applied to the Atlantis+ so they didn't need replacing.
The more expansive soundstage remains intact, which is the main thing I was worried about.
The Orchid+ is definitively better for Rock in my opinion, based on my limited experience, and to my particular taste (thanks, @schiit). I'd honestly likely prefer the Gungnir Multibit for Rock because it's the only genre I still prefer oversampling for, but I can't afford two nice DACs at home.
Classical and Jazz trade blows, but the more expansive symphonic music goes to the Orchid+. The Atlantis+ wins with intimate female vocals or calm acoustic guitar.
Overall, the Orchid+ is a bit more versatile than the Atlantis+ and is a small step up from the stock Orchid. It has the lovely euphony of the TDA1541A. Realized to its full potential? Hard to say. Maybe the Audial Model S is better, but I don't own one and can't directly compare them.
I also have a TDA1541A N2 chip on the way. It's supposed to be some sort of oddball late production chip that measures somewhere in the S1/S2/1998 range.