I've seen the question asked as to what type of Ethernet Cable to use Cat 5e or Cat 6. The first criteria to understand is that Sonos Ethernet ports are 10/100 Mbps (100 Megabits per second). That is the speed at which information (signal) flows.
Cat 5e Ethernet is capable of moving information up to 1000 Mbps (1 gigabit) and Cat 6 Ethernet at 10 Gbps (10 Gigabits per second). In the real world the theoretical speeds of Cat 5e and Cat 6 are affected by any number of factors which will limit those speeds to less than published. For the average consumer Cat 5e should be sufficient as the cable of choice. Cat 6 is most likely overkill; unless you are running an Enterprise Network which is more common in the business world. Another factor for choosing Cat 5e is that to date ISP's (at the consumer household level) offer nothing faster than 1 gigabit per second speed (1000 Mbps).
In conclusion; for Sonos, all things being equal (brand and strand quality) Cat 6 Ethernet Cable exceeds the basic requirement for a stable Sonos connection_where as Cat 5e Ethernet Cable will suffice. You will also save money in the process. For example_Bestbuy branded Dynex 6-foot Ethernet Cable: Cat 6 lists for $9.99 vs. Cat 5e for $4.99 an approximate 50% savings for the same performance with Sonos products.
There are always exceptions such as a "fire sale" for Cat 6 Ethernet cable at the same or reduced price vs. Cat 5e Ethernet cable. You be the judge and enjoy your Sonos!