most current version of 4k tv box

The HDMI cables are new.  The XG1 box is nearly 4 yrs old.  I stopped by our local Xfinity store yesterday, they are shipping a new one.  Hopefully that will help.  Do you have any insight to best practice for connecting to TV and Audio system?  Is it best to connect the box to TV, then use HDMI ARC to the audio receiver?  Or the reverse, connect the box to the audio receiver, and from there via HDMI to the TV?  Does that make any difference?

@user_ddvmtr Here is a great article about how to connect your audio system. Audio Connection Cables, Jacks and Ports for Your Comcast Equipment

@user_ddvmtr​ If your AVR can pass 4K video to the TV, then there's no difference on picture quality.  Sound should also be the same either way, although I've seen a few times where the X1 box sends 5.1 PCM, which will get downmixed to stereo over ARC.  (eARC can do 5.1 PCM.)  So, connecting to the AVR would avoid that complication. 

Thanks for the information.  Do you know...is there a difference between using DHMI vs a digital optical or coax connection for audio?  I have heard that the digital optical/coax supports 5.1, but not higher.  If I want to use Dolby Atmos with front height speakers, is HMDI required to pass the full 7.1 signal to the AVR?

@user_ddvmtr, those are all great questions, but we are not trained in that aspect, and I would hate to give you incorrect details. What I can say is I personally use HDMI for my audio setup and I have a 5.1 Dolby Atmos.