I haven't listened to the Stockholm, but I am not really enticed by it as it is largely the same as the Havana except that it accepts 192 KHz max input frequency vs 96 KHz with the Havana and also has asynchronous USB input and an added BNC input. There is at least one account by a Stockholm user that both DACs also sound nearly identical with standard resolution recordings. Async USB seems to be best handled by an external converter, the RCA SPDIF on the Havana can be easily replaced by BNC, and I'm not gung ho about 24/192 recordings as they are sparsely available and expensive. I am actually looking for a second Havana and if I run across a used Stockholm at a competitive price I might consider it.
I cannot understate how much the Havana can improve over its stock incarnation -- I mean many leagues better. Havana owners can probably all agree that it is not a highly detailed or dynamic DAC, but it is clearly the most detailed DAC I've had in my system now and maybe the most dynamic as well. It is really something special when you put very good parts in it. The costs add up (especially the teflon V-Caps!) and well exceed the price of DAC itself, but in the end it can easily stand up to, and I would imagine for many people beat, far more expensive units.
I enjoyed the Calyx a lot. It has a BIG presentation, quiet, quite detailed, great dynamics, with good weight and body, but a little too soft around the edges to be well rounded if you have eclectic tastes in music. The major detractor for me was that vocals have a diffuse quality about them as if your wall is singing and not focused like there is a person in the room. Still a pleasant and musical DAC.
The Octave didn't last very long in my system. It succeeded the Berkeley Alpha DAC Series 2 (a wonderful DAC) so it had big shoes to fill and it did a very respectable job. The most notable attributes were the clarity and separation. Very clean sounding and very good, natural tone. Good dynamics, particularly extended decay. I can see why this DAC gets such positive press, especially considering the price. However it is not without fault and for me the issues were that I found it somewhat flat sounding in terms of imaging and the highs could sound a little brittle compared to the BADA 2 (remember, 5-6 fold price difference). I think I could have lived with it if I had to, but I would also be fully conscious of its weaknesses, which is why it's always hard to take steps back. But then I tried the CuTF output caps in my Havana and immediately knew I had to go in that direction.
