No cable changes will get you a “better sound experience”. 

The cable that ships with the Beam gen 2 is already sufficient to carry any codec the Beam can deal with, no “upgrading” will make any difference. 

Yes and No.  First off I believe the cable that comes with the Beam is HDMI 2.1, correct?  Not sure a new cable is an upgrade.

Second, you need an HDMI 2.1 cable if you’re using eARC, but it does you no good if your TV isn’t eARC compatible.  As well, you aren’t necessarily getting better audio quality if your audio source isn’t producing the higher audio quality formats.  From the Beam’s FAQ:

Do I need a TV that supports HDMI eARC?

No. Beam (Gen 2) can connect to TVs with eARC, ARC, or optical outputs. For greatest compatibility, eARC is recommended.

If you connect to a TV with eARC, the Dolby audio formats supported include Dolby Atmos, TrueHD, MAT, Dolby Digital Plus, and Dolby Digital.

If you connect to a TV using ARC, the Dolby audio formats supported are dependent on your TV model and manufacturer. The TV may be capable of sending Dolby Atmos, Dolby Digital Plus, and Dolby Digital. An ARC connection cannot support TrueHD or MAT.

If you connect to a TV using the optical adapter, the Dolby audio formats supported are dependent on your TV model and manufacturer. The TV may be capable of sending Dolby Digital. An optical connection cannot support Dolby Atmos, TrueHD, MAT, or Dolby Digital Plus.

Thanks a lot for your responses.

My tv is eARC compatibility. So the cable of Sonos is ok for eARC, right?

The cable supplied by Sonos is fit for purpose and can carry lossless Dolby Atmos and TrueHD depending on source.

Please also see the Sonos reply in this thread regarding the cable supplied with the Beam and Arc: