Here it goes -
First of all, I make no claims of being an "audiophile", I don't have the money for that. Second, realizing that I am using two different cables, Signal for the NAD, Rat Shack gold for the Onkyo, I did realize that there might be a slight difference in sound. I did switch the cables on both and found slight to no difference on most sources. I will be changing all my cables to Signal in the near future, funds allowing, however.
Like I said before, my wife had the first comment, the unit being more quiet and clear, definitely so (I am so glad she has come to appreciate fine sound). I did notice a deeper soundstage right away. Plus more defined detail in musical notes in the instruments, especially high piano keys and voices. By a deeper soundstage meaning this. Before, with just the Onkyo, I could place instruments pretty well, either left, right or in the middle. Now I can tell you where they are in a row almost. The drums were the most noticeable. When they are "hit" you know that they are in the back of the stage/hall. Just by the way the sound is portrayed you know. My oldest classical CD is by Telarc, one reason I usually only buy Telarc classical BTW, Tchaikovsky's 1812 Overture with Capriccio Italien and "Cossack Dance" from Mazeppa. Played by the Cincinnati Symphony Orchestra with Erich Kunzel conducting. The NAD really brought this CD back to life! After having this so many years it's like it's brand new! With the cannon fire at the end of 1812 I cannot only place the cannons left or right, I can also tell which position they are in. Meaning, instead of noting 2 cannons on the left I can tell you which one is positioned closer to the center, very clearly. Not bad for a recording from 1979.
As far as jazz types of music go the most interesting thing I noticed was the bass drum. It's very clear how hard the drummers foot is hitting it. Soft, hard, whatever. I did notice this slightly on the Onkyo as well but not this much.
I only have one HDCD in my small collection, Michael W. Smith's Freedom. This is CD is really good and it was representative of what I call "modern" classical. As far as HDCD sounding much different from regular CD's there is a little difference but not much, IMO. At least in the different players, as the NAD has HDCD decoding and the Onkyo doesn't.
All in all as far as music goes the sound is not necessarily more detailed as the Onkyo but much smoother and defined. I didn't realize how harsh the Onkyo sounded, especially on the high piano notes and higher voice recordings. It was almost "scratchy" compared to the NAD. More natural would be a good word for it. The music seemed more real, you could sense the passion of the person playing/singing. Is the Onkyo that much of a slouch? Not in the least! Most people who don't care that much for music listening over movies are best to stay with a DVD player. But..., the Onkyo DVD player I have was noted for it's musical qualities.
I don't use the 12 Volt trigger since the wife tends to listen to the radio during the week so I couldn't justify having it on and not being used for hours at a time. It will go on stand-by, which is were I leave it when not in use, but will only do so with the remote. This is one thing I do not like. They should have put a stand-by button on the front.
The remote has to be the cheapest remote I've ever seen but it works fine. Like a friend of mine said, it's better to go cheaper on the remote than the player.
Suppose that's about it. I am glad I made the purchase I did. Would I have bought a different, more expensive player had I had the money? Sure! I had my eye on the Krell but at almost $3000 the wife was turning red when I just brought it up! Within my means and for the price, I believe this to be a quality player with very musical qualities. As for reliablity, time will tell, as I've never owned anything NAD before.
I believe the ulimate test for any equipment is classical music, well recorded. I did, however, include some different sources as everyone is different in their desires. As far as some CD's sounding bad on the Onkyo (bad recordings), they did sound worse on the NAD. It might be time to sort out some and have a fire in the fire pit in the back yard....
Don't forget, results may vary depending on each ones own system!:D