Which Synology for an NVR

Hi All,
I’ve currently got a QNAP TS-253-Pro which I’m currently using as an NVR only.
I’m looking at replacing this with a Synology NAS to benefit from the better firmware and NVR Solution.
I’ve got a DS212j and it got after DSM5
What do people recommend when it comes to the Synology Hardware for an NVR.

I’ve spotted a few used models (DS216j, RS814+) but my main worry is how long are they going to be supported.
I then look at new and don’t really want to spend over £200 so then looking at (DS120j, DS118, DS220j or DS218Play),
I have spotted the NVR1218 but this isn’t compatible with DSM7.

I would not get one that does in not still under support and make sure it supports Surveillance station version 9 which is the latest.

Thanks Tom,
Will keep a look out.
Going to look into converting the QNAP into Truenas and put zone minder on it