The Nuforce Icon is MUCH better as a speaker amp than as a headphone amp. And it is a great little integrated amp with 3 inputs (USB, RCA, 3.5mm) and 3 outputs (12 watt, 3.5 mm preamp, and 3.5 mm headphone). Even the Pre-amp out sounds better than the headphone out and is on par with the speaker out - very detailed and natural and transparent. The preamp out does not seem to degrade the signal passing through the Nuforce and going into other amps.
The Icon headphone out is not bad, but it is slightly veiled and more on the level of an iBasso D2 Boa, rather than as good as the iBasso D3/Pico/Predator. It is a little below the Travagans Red now that I have spent more time with it, but I use mine as speaker amp to drive my SRD-7 Pro electrostatic transformer and it beats the Red in that capacity without question. The bass is more commanding and it controls the drivers better.