Hi apollophono,
I have had Onkyo HF player on and off my iPhone for a couple of years now. I say on and off because where I am using it, in a convertible, I don't get a lot of quality sound time. I do want to have the best sound possible. So I had a new head unit, amp, and speakers put in to replace the aging factory stuff. The sound is ok and I can hear it when driving around over 50 mph. Not that I drive around over 50 mph all the time... It plays hi rez stuff which iTunes can not do. That is another plus though I don't carry a lot on the phone at this time. I have not tried it on the main stereo at home as I use JRiver. I recently got a Schiit Wyrd which allows me to use the iPhone as a source and do on occasion. So I guess I will try it at home at report back. Thanks for the post.
Best,
Blu99Zoomer