Note that you have to have a physical DVR box to record 5.1 surround sound. Some of the X1 configurations do not include a DVR but record in the cloud - and then you will only have stereo sound. When you start to play a recording you should see 'dvr' in the lower left or a cloud symbol while the timeline and controls are showing.
Good news here. Jimmy comes through at the advertised 5.1. As U state, preponderance of sound is from your center; I get a decent volume all around. My receiver advertises Dolby 5.1 is being received.
Oh, and yes I do have a DVR in my X1 box.
Also fiddled around last night and found a Star Wars moov, rear sound was noticibly weak, typical of most content from cable. Still not satisfied with the experience.
Thankx for the conversation and have a great holiday.