Synology 418play VS 918

Morning all, first post here. I am building out a home theater and realizing I want to also incorporate my media from DVD,Bluray, and 4k blu ray to media on a NAS. I have never done ripping but going to learn my way on this. I also would like to use the NAS for backup for my computers as well as a server for music for Sonos. Whats my best bet between the 2? I have read abunch of threads on it and the 918 has quad processor and comes with more ram. What have you guys found is better to server media etc…

Bill