John,
The Nuforce HDP does indeed open up its soundstage and depth after about 125 hours.
At first listen, it was unapologetically clean and stark, without much warmth in the middle.Listening to Bela Fleck's African miniatures in "Throw down your heart" the HDP shines with a remarkable clarity and disarming vocal artistry which crawls intimately down your ears and tickles your brain with a complex recitative of bewitching vocal phrases. No doubt, the high quality source signal and color here is complimented by the strengths of the amp section and the reliably clean Dac signal. The pleading and whailing singing of "DJorolen" breathes heated and palpable emotion without any sound-stage or floor noise.
The more you open the gain, the more detail and dynamic contrast emerge.
I'm now listening with 200 hours on the HD600s with Cardas and the sound depth has increased noticeably.
My Audio gd FUN should arrive here on Friday and I will start some obsessive burn-in hours on both to compare soundstage, depth, detail, musical range and color. Someone please give me a valium or I'll never go to sleep.