I am very happy with my new iFi Zen DAC 3. I use it as a desktop headphone DAC/Amp to power Sennheisser HD660S2 headphones with a balanced cable. I also used my much more reasonably priced JBL wireless/wired headhpones (Tune660) on the unbalanced jack with good results as well.
Playing through a variety of music the iFi implementation of the Burr-Brown chip provides a robust and satisfying experience. The incredible depth, color, range and dynamics(21 LU) of St. Saens Symphony No. 3 (organ) was clear and real from the deepest rumble from 32 foot organ pipes to tinkling rain bells and crashing cymbals with strings that sounded authentic and did not seem muddy or contrived.
My experience with Dire Straits, Carly Simon, Pink Floyd, 10,000 Maniacs, John Denver, Heart, Pet Shop Boys, Morrisey, Joe Walsh, the list goes on, from Classical to classic rock to new wave, country, electronic, folk, and choral was the same - superb. The genre shifted as did the formats from basic 44/16 and 192/24 flac, DSD 64 and 128, MQA, and even older mp3's sounded great with instant transition between formats
I typically use Roon to manage playing music that is sourced locally or streamed from Tidal.
I have not used the ifi Zen DAC 3 with a separate amp and speakers.
I also purchased the separate iFi SilentPower iPower2 - Low Noise DC Power Supply with this item. It turns out that the DAC can operate on the power provided over USB and sounds great, but using the separate power supply really opened up and fortified the sound in direct comparison.
The iFi Zen DAC 3 is a great sounding, good looking, solid desktop headphone DAC/Amp.