You say you don't think much of the Yamaha A-S500 amp, but you don't actually say what it is you don't like about it.
I use the headphone out most of the time and play CD's / lossless through ipod classic connected to the CD-S300's (CD player) ipod port.
The sound is Alive: It is powerful, energetic, clean, separation is incredible and in a word, spectacular!
Can you tell us what it is you object to about the Headphone Out. I would be interested to know what you actually know about the amp.
Just putting this out to those who criticise, if the criticism is valid, fair point, but at least make your case as to why you are critical.
I have a theory: A lot of people believe that because they have spent an absolute fortune on something that sound the same as something that costs a tenth of the price they have to justify their purchases by putting down anything that is not as expensive, even if it is as good or even better than what they were persuaded into buying and wished they hadn't.
Quality is quality whether it's cheap or expensive, Junk is junk even if it cost a fortune.
Tell us your honest thoughts on the Yamaha A-S500, as I for one am amazed that you have criticised such an outstanding example of audio excellence.
Criticism without foundation is just sour grapes.