Wanting to get to 100TB usable

Hello all, as the title says, I’d like to get to 100TB usable capacity. My current setup is 6x 8TB WD Reds in a RAIDZ2 array under TrueNAS. Usable is about 25TB give or take.

I have roughly $1500 to spend to make this happen but that must include the cost of a new case and drives. Current case is a Node 804 which will be retired. Current mobo is a Supermicro X9SCL with a E3-1220 V2, 16GB of RAM (will upgrade to 64 after this storage upgrade). LSI HBA but can’t remember the model off the top of my head.

Looking to move to a CSE-846 or 847, but not opposed to a more storage dense solution with an 826/827 or 836/837.

I’d like to keep the current drives for now but I’m not opposed to other options. I’m thinking adding either 2x RAIDZ2 arrays with 10TB drives or 1 with 20TB drives.

Does this seem reasonable or feasible for this price range? I’ve found manufacture refurb 10TB drives on eBay but I’m not sure of quality or reliability of seller.

Open to any and all suggestions.