Need Help Selecting Synology Rackmount NAS - Q1 2021?

I will be looking for a new Synology rack mount NAS in the first quarter of 2021. I have a a DS3615xs offering ~87TB available storage (10 x 12TB drives RAID 6). About 50TB is in use. That machine runs a Plex server offering movies, TV, music and audiobooks. It also runs Cloud Sync to copy data to Google Drive, Hyper Backup to backup to a DS1010+ every six hours via Rsync, Cloud Station, and Synology Chat. The DS3615xs has a number of CIFS shares on it as well as an NFS datastore for vSphere. It's connected via 10G Ethernet.

I want to replace that unit with something higher-performing, newer, and rack mountable, since all my servers and most other devices are now in a rack. The DS3615xs would sit on top of the rack and serve as a backup target or node in a two-node Synology cluster, if possible.

I am looking for 10G connectivity, M.2 NVMe caching and good performance with NFS and iSCSI as shared storage for a vSphere cluster.

Can you assist with a recommendation? Thank you.

Okay, I got no hits or answers on this, so I went out on my own.Late last year, ahead of schedule, I bought a RackStation, an RS1619xs+ with a RX1217 expansion unit. Beautiful kit, both. I replaced the fans in the RS1619xs+ with Noctua fans as the stock fans were loud and changed pitch and volume several times a minute.I put 4 x 14TB drives in the NAS made them BTRFS on RAID 5. When the expansion unit arrived, I added 5 more 14TB drives and started a conversion to RAID 6, which, almost two month later is 68.91% complete (roughly one percent per day). When the conversion if finished, expected during the first week of May, I have two 2TB Samsung M.2 SSDs to add as cache. There is already an Intel 10G card installed.Over the course of a few sales, I've stocked up on shuckable 14TB drives, enough to fill all 16 drive bays, but decided to wait until space becomes scarce before putting in more drives. Silly to run them, shorten their lives and use electricity if I don't need the space.I'll continue to use the DS3615xs as primary storage for network shares and for Plex, even though the RackStation is a Xeon whereas the DS3615xs is a Core i3.The RackStation will get the hundred or so vSphere VMs that I have. It's already is a target for Hyper Backup for the DS3615xs. Conversely, the DS3615xs will become a target for VM backups and replication from the RackStation, once the VMs are moved to it.All lots of fun! I highly recommend this stuff!Oh, the NAS, expansion unit, rails, and cache SSDs were purchased at B&H, on their store card, tax free. The hard drives were acquired through Best Buy at about $14.75/TB after tax. Shopping is as much fun as buying!