Best upgrade?

[Enquiries]

Hi! Thanks for an excellent site! I would like some advice on what NAS upgrade I should look at. Currently I am on a Synology 214+ where I recently got 2 x N300, 8 TB NAS disks. But I realize that to be able to run Nextcloud or any other software that process images and videos I really need more CPU. I have a lot of personal video in 4K stored and I want to be able to share that to friends and family. I like the DSM but would be fine using the QNAP software too. Thankful for any advice on what model with most bang for the buck. I guess upgrading the RAM on any model would be recommended?
I was looking at QNAP TS-253D-4G or Synology DS720+
Thanks in advance.