What specific issues are you experiencing or what do you expect to gain from the “upgrade”?
Not a lot of significant differences from I can see.
For MP3 storage and Downloading, you probably won’t see any difference.
For Container Station, additional ram or a significantly better CPU would likely be your best option, but it depends on how many and what is running in the containers as well.
IMO, if you are going to invest in upgrading to a new NAS, purchase the highest performance one you can afford. And get as much memory as you can afford as well (3rd party - not QNAP’s).
Only you can determine what that amount is. But you will be happier in the long run if you invest as much as possible in the NAS. Just because a NAS that cost a few hundred dollars works, does not mean it will work well.
If you plan on running much in Containers, transcoding in Plex, etc. then you may want to consider a NAS with a bigger CPU than a Celeron. Just saying…
The TS-264 is a $465 NAS. You are looking to buy a "server” basically. How much did you spend on your PC/Mac?
Again maybe this is what you can spend. That’s fine. But don’t get that model just because it’s “cheap.”
I agree with this, after upgrading my personal NAS from Celeron to i3, all operations became much smoother.
For MP3 Storage and Downloading, I think there is no help even upgrade to i9.
For the Container Station, there should be no difference between 253D (Celeron) and 264 (Celeron)($465), maybe AI642 (RK3588)($649) might be of some help, but I don’t know how much it could improve things.