New Syno or DX517

[latsAP]

Hi all, 

I'm a photographer and have been using a DS1513+ and a DS1819+ for the last 10 years for the majority of my storage, daily backups etc.

The DS1513 is still taping along and working fine.  I syncs with my dropbox and stores all the nightly backups.

The DS1819 has the photography Archive and some working files.  (it has SSD read write caches and the 10GBE nic)
I'm running out of space on it (8x16gb hdds)

I need to increase my archive storage.
I don't need remote access, but I do need speed for large photography files (20gbs) and raw video footage.

I see my options as:

1. purchasing a DX517+  with 5x 20tb drives and extending the ds1819+ with an extra volume for older less accessed storage.
   
2. purchasing a DS1821+ with 5x 20tb drives and 10gbe NIC that would replace the 1819+
   1819 would be used for older storage and 1821+ for more current (move SSD cache over to 1821+)
   1513+ would remain as a backup unit.
   
3. Leave Synology for another vendor.
   

I've been pleased with Synology for the last 10 years as my needs are quite simple, but their lack of development of units in my space has me a little worried for future support.

I'd be interested in any advice or commentary on future strategy.

Thanks!