I have the Zu ODW speakers as well (with tweeter caps updated to Miflex copper foil) and auditioned the SET 120 about a year and a half ago. Also had a buddy with the bigger brother to the SET 120 bring it over to compare. They had a very similar sound, for sure. The SET 120 sounded great with the ODW. My buddy preferred it to my Odyssey Kismet stereo amp, but after a more extended comparison during the trial period, I ultimately preferred the Kismet amp. But I easily could have lived with the SET 120 and there were some aspects of it that I preferred to the Kismet.
In my opinion, it's a great match to the ODW. It has a bit warmer presentation than my Kismet (though I was using Furutech fuses on the Kismet, which thin the sound just a touch while adding transparency - and the SET 120 just had standard type fuses), which gives it a nice solid character in the important power region for frequencies - great for rock, and transparent enough for all types of music. A nice natural tone for sure. And while not the ultimate in transparency, details were very good and certainly didn't feel anything was missing while listening. The overall frequency balance and tonal character did remind me of the sound of my Line Magnetic 518ia 845-based SET tube amp, though I wouldn't say that the SET 120 sounds like a tube amp. I'm just saying the 845 amp also has a similar strength in the power region and similar general warmish tone. And frankly, my Line Magnetic amp just rocks the ODWs - very addictive sound.
So again, I think the SET 120 is a great combo with the ODW. That said, the ODW are crossoverless and have the potential to show the benefits of more transparent amps too. It all depends on your priorities and how you balance those priorities along with the other components in your system.
I have been shopping for a streamer solution myself like the Cambridge you have, the Bluesound Node, and others below around $2k. From what I've read, the Cambridge is highly respected at the price point for its level of detail retrieval and a bit more natural sound than the Bluesound when used as a full front end rather than just wireless endpoint. But I've also read that the sound is a bit thinner than higher priced units can be - makes sense, as some things have to give at lower price points. Given this, I suspect the warmish tone of the SET 120 would fit very well in synergizing the Cambridge with the ODW, which could be fatiguing if fed a thinner or brighter sound.
As for control amp version vs power amp version, just keep in mind the control amp has a higher gain, I believe. So you might be using more attenuation with your high efficiency ODWs with the control amp than with the SET 120. That said, I would think the control amp's internal volume control would be preferable to your Cambridge streamer's internal attenuation. My understanding is that the Cambridge uses software attenuation, which is lossy, so you wouldn't want to be using a lot of it - much more than a few dB of attenuation could lead to significant loss of sound quality.
