I normally listen to music at very low volumes, but when I do turn up the volume, the HDP has point in the range where the bass seems to remain the same volume, but the mids and trebles continue to increase to the point where the sound is blaring, but the bass is not where I want it to be. With the Asgard, the bass scales very nicely with the higher frequencies, and I get my full satisfaction with those occasional volume increases.
Also,I don't necessarily subscribe to the notion that bass damping is a significant factor with the typical resistance-controlled headphone transducer, but the HDP has a 10Ω output impedance compared with the .5Ω of the Asgard. People have been tossing around a minimum ratio of 8:1 for optimal configurations, and the 25Ω Denon line of headphones do not match well with the higher output impedance of the HDP. I understand why it is important for loudspeaker low frequency response at max motion reactance, but I'm not convinced this applies to most headphones.
Anyway, the Asgard is crazy cheap, and it looked to pair well with my D5000, so I opted to give it a try. I think it sounds better than my HDP, overall, and I needed a DAC, so the HDP filled that role nicely. The HDP is versatile, but I only use the digital optical output, and I use an optical switch to control the 3 separate input devices going into it. I would recommend the Asgard to anyone that could make use of it. The confidence of the build quality with the 5-year warranty was the icing on the cake for me. I would only recommend the HDP if the versatility of the inputs could be taken advantage of, as there might be better options available at the same price if you just need a DAC and Amp with a single source.
Granted, the difference is not major, but I have what I have now, and I am using the equipment in a manner that provides the absolute best quality for me. Live and learn. If I could, I'd start all over and go with the Burson amp, or the newer DAC/amp; but, for the cost, the benefits would not be nearly as drastic an improvement from what I have now. More often, I find myself wanting to listen to "just one more song" before I shut everything down and hit the sack at night. I didn't get this same level of desire with the HDP, and I had the HDP for quite some time before I got the Asgard. The Asgard is better with the D5000 to me.